Every season, a few bullpen arms emerge (or re-emerge) from obscurity, providing their clubs with excellent relief work for a bargain-basement price. Today I’d like to highlight three such hurlers. Each experienced big league success in the past, but had fallen on hard times lately. Without further ado, here are the ‘pen performers who have returned from the dead in 2010..

J.J. Putz, White Sox

Signed: December 2009 — 1 year, $3 million

A nondescript major leaguer with the Mariners in 2004 and 2005 (a combined 0.1 WAR in 123 innings), Putz terrorized hitters in the late frames the following two years. With a fastball that crept up to the mid-nineties, a mid-80’s slider and an upper-80’s splitter, he led all relievers with 3.6 WAR in 2006 and followed up with 2.3 WAR (a top-10 mark) in 2007. Over that two-year span, Putz owned an 11.16 K/9, 1.56 BB/9 and a 2.50 xFIP (best among relievers).

The 6-5, 250 pound righty’s reign as bullpen king, however, was short-lived. Plagued by rig cage and elbow ailments in 2008, Putz still missed scads of bats (10.88 K/9) but lost the zone often (5.44 BB/9). He hit the DL twice and finished with a 4.13 xFIP and 0.6 WAR. Swapped to the Mets as part of a three-team deal in December of ’08, Putz tossed just 29.1 innings for the Amazin’s last year before undergoing season-ending surgery to remove a bone spur from his elbow. He never looked right, compiling just 0.1 WAR with as many walks as punch outs (5.83 K/9 and BB/9 apiece).

Picked up by the White Sox over the winter, Putz is dealing in 2010. He has a 2.28 xFIP and 0.6 WAR in 21.2 IP, whiffing 11.63 per nine innings and issuing 1.66 BB/9. During his big league career, Putz has thrown his fastball about 70 percent of the time. This season, however, he’s going to the heat 52 percent of the time. The 33-year-old is relying heavily on his splitter (about 35 percent), and he’s getting a ton of swings on pitches off the plate and plenty of whiffs. Among relievers with 10+ IP, Putz places tenth in outside swing percentage (37) and 20th in swinging strike rate (12.8 percent).

Joaquin Benoit, Rays

Signed: February, 2010 — minor league deal, $750K with $500K in incentives

A swingman with the Rangers from 2002-2005, Benoit transitioned to relief full-time in 2006. Over the next two seasons, he owned an 9.58 K/9, 3.67 BB/9 and a 4.01 xFIP, racking up 1.4 WAR in ’06 and two wins in ’07. Benoit had long dealt with injury problems — according to the Baseball Injury Tool, he was sidelined with elbow inflammation in 2003, shoulder tendinitis in 2004, and shoulder and elbow tendinitis in 2005. But he was healthy and effective for the Rangers for those two seasons.

It didn’t last, though. Bothered by shoulder soreness in 2008, Benoit slogged through a sub-replacement-level season (-0.2 WAR). Joaquin K’d 8.6 batters per nine innings, but walked seven per nine with a 5.71 xFIP. He underwent rotator cuff surgery in early 2009 and missed the entire season.

The Rays took a flyer this past winter, and it’s paying off. Benoit, 32, shredded Triple-A hitters with Durham to begin the 2010 campaign (9.2 IP, 17/3 K/BB) and he’s doing the same in the majors. He’s got 12.64 K/9 and 2.3 BB/9 in 15.2 innings, with a 2.29 xFIP and 0.4 WAR. Throwing his fastball harder than ever (93.7 MPH average) and mixing in mid-80’s sliders and low-80’s changeups, Benoit has an obscene 16.4 swinging strike rate, a number that is tops among MLB relievers.

Clay Hensley, Marlins

Signed: May 2009, minor league contract. Re-signed for $425K in December 2009

Hensley’s career highlight is a 2.1 WAR season for the Padres back in 2006. In 29 starts and eight relief stints covering 187 innings, Hensley used a kitchen-sink approach to post a 4.34 xFIP. Using an 88 MPH sinker, a low-80’s slider, a mid-70’s curve, and a low-80’s change, Hensley didn’t miss many bats (5.87 K/9) and his control was average (3.66 BB/9), but he made up for it with strong ground ball tendencies (53.9 GB%).

Injuries wrecked his next two seasons, as Hensley succumbed to labrum surgery in September of 2007. Before going under the knife, he served up Barry Bonds‘ 755th career home run and then got booted to the minors the next day. Hensley had a combined -0.3 WAR over the ’07 and ’08 seasons.

The Astros signed him to a minor league deal prior to 2009, but released him. The Marlins scooped Hensley up and stuck him in the Triple-A rotation, where he posted rates of 6.47 K/9, 3 BB/9 and a 3.73 FIP in 114 innings. While he lost out on a rotation spot this past spring, the 30-year-old has been a revelation in relief for Florida.

He’s still a soft-tosser (89.1 MPH), but he has gone to the fastball under 50 percent of the time. Instead he’s going to a slow curve (71-72 MPH) and changeup over 20 percent each, while tossing the occasional slider as well. Hensley has a 3.10 xFIP and 0.8 WAR in 32.1 IP so far, with a whopping 11.69 K/9 and 3.9 BB/9. Clay has retained his ground ball rate, too, with a 50.7 GB%.

As these three show, there are values to be had on the relief pitching market. A team can cobble together an effective ‘pen without shelling out a high seven-figure annual salary and holding a flashy press conference.

Little has gone right for the Chicago Cubs this season. The club’s starting pitchers boast the second-best xFIP in the National League and the defense isn’t too shabby, either (fifth in UZR). Unfortunately, those strong performances have gone to waste due to mediocre relief pitching (11th in the NL in xFIP) and offense (12th in wOBA). Even after last night’s 1-0 victory over the White Sox, the Cubs have a 28-35 record. At 7.5 games back of the division-leading Cardinals and eight games behind the Dodgers in the Wild Card chase, the Cubs have less than a seven percent shot of making the playoffs, according to CoolStandings.com. Yes, Lloyd, I’m telling you there’s a chance. It’s not looking good, though.

While there are many reasons as to why 2010 is shaping up to be yet another aggravating season in Wrigleyville, Marlon Byrd surely isn’t among them. The 32-year-old center fielder, inked to a three-year, $15 million deal over the off-season, is enjoying a career year.

Byrd’s batting .333/.375/.543, with a .400 wOBA that ranks in the top 20 among qualified big league hitters. He’s not walking (3.6 BB%) or whiffing (13.7 K%) much — he’s just racking up extra-base hits and getting some fortunate bounces on balls put in play. Byrd’s ISO is a career-high .209, while his .354 BABIP is 31 points higher than his expected BABIP and 29 points above his career BABIP in the majors. Defensively, Byrd has rated as average to slightly below average in center during his career. But he owns a +17.3 UZR/150 and +10 DRS in 2010. With three Wins Above Replacement, Byrd places seventh among all MLB position players. Not bad for a guy whose career has been on life support a couple of times over the years.

A Georgia prep star in baseball and football, Byrd attended Georgia Tech but suffered a devastating right leg injury — three procedures were performed on the leg, and at one point doctors considered amputation. He transferred to Georgia Perimeter Junior College, where his health and stock improved enough for the Phillies to pluck him in the 10th round of the 1999 draft.

Byrd emerged as a top prospect, cracking Baseball America’s top 100 list prior to the 2002 and 2003 seasons. He amassed 3.5 WAR rookie season in ’03, proving himself an asset at the plate (116 wRC+) and in the field (+5.1 UZR/150 in CF). At 25, Byrd looked poised to be a quality contributor for the Phightins for years to come.

But then he imploded. Byrd plummeted to -1.6 WAR in 2004, and followed that up with 0.9 WAR in part-time play during a 2005 season in which he was traded to the nascent Nationals. He split 2006 flailing in Washington (.294 wOBA, 0.4 WAR). But he hit fairly well in Triple-A (.369 wOBA). Byrd latched on with the Rangers prior to 2007, signing a minor league pact. After raking with the RedHawks to begin the year (.424 wOBA), Byrd was called up to the big leagues and proceeded to revive his career in Arlington.

From ’07 to 2009, Byrd was Mr. Average — he had 2.3 WAR per season, with a park-and-league-adjusted wOBA 14 percent above the norm (114 wRC+) but a glove that was a couple runs below average per 150 defensive games. CHONE had Byrd pegged for 2.6 WAR in 2010, a mark that he has already exceeded. Barring injury, he’ll easily surpass his rookie WAR total, too.

Odds are Byrd won’t remain one of the absolute best players in the majors. But ZiPS projects a .367 wOBA for the rest of the season. That, coupled with average D, would continue to make him a valuable starter. Byrd has taken a circuitous route to big league success, but he’s looking like a free agent coup for the Cubs.

For most of his major league career, Jose Valverde has relied upon pure, unadulterated power to close out games. Delivering sizzling fastballs from a calm, unhurried motion that contrasts with the wild leaping and fist pumps that follow the recording of the final out, Valverde has punched out 10.7 batters per nine innings, issuing 3.62 BB/9 and posting a 3.48 xFIP in the bigs.

The former Diamondback and Astro inked a two-year, $14 million contract with the Detroit Tigers this past winter, with a $9 million club option for the 2012 season. Papa Grande hasn’t been scored upon since April 7th, a stretch of 23 appearances. Clearly, Valverde has been the beneficiary of good fortune — he’s got a 0.37 ERA, due in large part to a Houdini-like .136 BABIP, a 96.6 percent rate of stranding base runners and a 7.7 home run per fly ball rate. For comparison, Valverde’s got a career .280 BABIP, a 79.3 left on base rate and a 10.4 home run per fly ball rate. But his xFIP, 3.59, is right in line with his previous work. Same old Valverde, right?

Not really. In the past, the 6-4, 250 pound righty has been all about the fastball. He threw his heater in excess of 80 percent in 2005 and 2006, and used the pitch more than three-quarters of the time over the 2007-2008 seasons. However, there’s a clear change in Valverde’s pitching approach as of late:

(note: his Pitch F/X numbers don’t show the same changes in pitch usage. However, given that the pitches Pitch F/X classifies as fastballs have decreased several MPH this season, with a sharp decrease in vertical movement, I’m inclined to believe the system is lumping a lot of splitters in with the fastballs.)

After gradually decreasing his fastball usage in favor of a mid-80’s splitter over the past few seasons, Valverde’s percentage of heaters thrown has fallen sharply in 2010. He’s now tossing his fastball a little over half the time, going to his tumbling off-speed pitch over 44 percent. Valverde’s fastball sat at 93-94 MPH when he was airing it out with great frequency, but the pitch has parked at 95-96 MPH more recently.

The result of Valverde’s shift in pitching philosophy? Far more contact and ground balls than in years past. This season, opponents are putting the bat on the ball against the 32-year-old stopper 79.1 percent of the time, compared to a career 70.1 percent average. Valverde’s swinging strike rate, 14.4 percent during his career, is just 7.9 percent in 2010. His walk rate (3.7 BB/9) is basically unchanged, but his 6.66 K/9 is by far the lowest mark of his big league tenure.

While he’s not missing bats, Valverde has become an extreme ground ball pitcher. With a 68.3 GB%, Valverde trails only San Diego’s Ryan Webb and Atlanta’s side-arming Aussie, Peter Moylan, among qualified relievers. That’s quite the contrast to his career rate of grounders, 39 percent.

Amazing luck aside, Jose Valverde’s results are right in line with his previous work. But the process behind those results has been drastically different. Rather than employing a fastball-centric, high K strategy rarely involving infielders, Valverde is going off-speed often and burning worms like few others.

Boston’s bullpen is struggling this season. Collectively, Red Sox relievers have a 4.68 xFIP, besting just the Indians, Royals and Angels among American League clubs. The only Sox reliever with a sub-four xFIP is Daniel Bard, at 3.29.

You may be surprised to learn that Jonathan Papelbon, he of 2.6 Wins Above Replacement per season as a full-time reliever from 2006-2009, is among the most egregious offenders.

In 24 innings pitched, the famed river dancer is walking a tight rope — his 3.00 ERA doesn’t look so bad, but his xFIP sits at 5.02. With -0.3 WAR, Papelbon has arguably been the least effective of Boston’s bullpen options.

Papelbon has a career-low 7.13 K/9 and a career-high 4.5 BB/9. He’s getting swinging strikes 11.1 percent, still above the 9.3 percent average for MLB relievers but below his 13.3 percent career average. The 29-year-old is also putting fewer pitches within the strike zone — 48.2 percent, compared to a career 53.6 percent average. When Papelbon does throw a pitch in the zone, batters are putting the bat on the ball more often. His in-zone contact rate is 89 percent, well north of his 81.9 percent figure as a major leaguer. If Papelbon’s batting average on balls in play were closer to his career .275 mark than his current .198, his struggles would be more apparent.

Sample size caveats apply, but 2010 continues a clear downward trend in the effectiveness of Papelbon’s fastball. During his career, Papelbon’s heater has been one of the best offerings in the game. His mid-90s gas has been worth +2.07 runs per 100 pitches. However, that fastball hasn’t been near as dominating lately:

Papelbon’s Run Value Per 100 pitches with the fastball, by year

2005: +0.69
2006: +3.24
2007: +3.29
2008: +2.21
2009: +1.49
2010: -0.34

Papelbon had the highest fastball run value/100 pitches among relievers in 2006. He placed second in 2007 and fifth in 2008. Last year, he still managed to sneak into the top 20. But this season, his fastball has been about as valuable as those of Danys Baez and Kanekoa Texeira.

Trip Somers’ texasleaguers site has three years of Pitch F/X data on Papelbon. There aren’t any large changes in terms of velocity or movement, but the strike, swing and whiff rates on Papelbon’s fastball are heading in the wrong direction:

2008: 71.3 Strike%, 56.3 Swing%, 11.5 Whiff%
2009: 67.5 Strike%, 51.8 Swing%, 10.4 Whiff%
2010: 67.0 Strike%, 49.7 Swing%, 10.0 Whiff%

It’s dangerous to infer too much from a few months of poor pitching from a reliever. But Papelbon’s performance as Boston’s closer has gone from awesome (2.78 xFIP from ’06 to ’08) to acceptable (3.98 xFIP in ’09) to replacement-level.

The odds that he continues to at this pace are very low — Papelbon has a long track record as one of the best relievers in the majors. But if the Red Sox are going to overcome New York or Tampa and snag a playoff spot, they’ll need their stopper to pick up the pace.

Before there was Steven Strasburg, unstoppable pitching cyborg or Bryce Harper, then-16-year-old Sports Illustrated cover boy, there was Matt Wieters. A switch-hitting, power-hitting force with enough athleticism in his 6-5, 230 pound frame to remain behind the dish, Wieters was selected out of Georgia Tech with the fifth pick in the 2007 amateur draft.

At the time, Baseball America said that Wieters could eventually “post averages near .280 with 30-homer potential in the big leagues,” and that despite his stature, he possessed “soft hands, good footwork and well-above-average arm strength, as evidenced by the 96 mph heat he has shown from the mound.” The $6 million man proceeded to terrorize minor league pitchers, batting a combined .343/.438/.576 at the High-A, Double-A and Triple-A levels. He also rated well defensively, according to Sean Smith’s Total Zone numbers.

Called up to the majors late last May, Wieters went on to post a .288/.340/.412 line in 385 plate appearances. That might not look off-the-charts good, but a .330 wOBA from a 23-year-old catcher, in the AL East, is extremely impressive. In four months of playing time, Wieters racked up 1.6 WAR. Heading into 2010, CHONE projected Wieters to rake to the tune of .289/.355/.460 (.356 wOBA), adding a couple of runs in defensive value while compiling 3.9 WAR. That’s the sort of production worthy of a Chuck Norris-style facts page (did you know Scott Boras hired Matt Wieters as his agent?)

Instead of building upon his successful rookie campaign, Wieters has stumbled somewhat over the first two months of the 2010 season. In 194 trips to the plate, he’s hitting .240/.314/.337, with a .290 wOBA. He’s holding his own defensively, rating as slightly above-average in controlling the running game after being a couple runs below average last season, but Wieters’ 0.5 WAR falls well short of his lofty preseason forecast.

Part of Wieters’ mild offensive showing can be explained by a .292 batting average on balls in play, down from last season’s .356 mark. His expected BABIP, based on his rate of home runs, strikeouts, stolen bases, line drives, fly balls, pop ups and ground balls, is .324. Still, Wieters’ current plate approach isn’t conducive to putting up robust numbers with the lumber.

While Wieters’ walk rate has increased from 7.3 percent in ’09 to 9.3 percent this year, his plate discipline hasn’t been as sharp. At first glance, it looks like he has become more selective — Wieters swung at 47.2 percent of pitches in 2009, but just 43.1 percent in 2010. But, it’s the type of pitches that he’s going after that’s concerning. In ’09, Wieters chased 25.7 percent of pitches thrown outside of the strike zone. This year, he’s hacking at 29.7 percent of out-of-zone pitches. He took a cut at 70.2 percent of in-zone offerings in ’09, but just 59.2 percent in 2010.

The MLB averages for O-Swing and Z-Swing differ between the two years, but even as a percentage of the league average, Wieters is swinging at more would-be balls and keeping the bat on the shoulder against more strikes:

Chasing more junk pitches and watching more in-zone pitches go by isn’t a recipe for offensive success. Wieters’ first pitch strike percentage, 53 last season, has climbed to 63.9 percent in 2010 (58 percent MLB average). He hit a ground ball 41.9 percent in ’09, but he’s chopping the ball into the grass 49.3 percent in 2010. That’s obviously not going to help in the power department, and Wieters’ ISO has dipped from .124 to .097.

All of this sounds pessimistic, but it’s important to remember that Wieters just turned 24 at the end of May. He thrashed minor league pitching, earning glowing scouting reports. He was a league-average hitter as a rookie playing the most physically taxing position on the field, in the game’s most competitive environment. Wieters’ rest-of-season ZiPS projection calls for a .275/.342/.413 triple-slash, with a .336 wOBA. Many teams would be thrilled to get that sort of production out of a competent defensive catcher. While he must hone his strike zone control, there’s still plenty of time for Wieters to reach those star-level expectations.

This past December, the Toronto Blue Jays ended a 15-year relationship with Roy Halladay by shipping him to the Phillies for a bounty of young talent including RHP Kyle Drabek, C Travis d’Arnaud and OF Michael Taylor (who was then swapped to Oakland for 1B Brett Wallace). Predictably, Doc is dominating in the Senior Circuit — in addition to tossing a perfect game against Florida on May 29th, Halladay leads the universe in starting pitcher WAR (3.2) and xFIP (2.93).

But you may be surprised to find that without Halladay, the Jays still boast one of the best starting rotations in the game. Collectively, Toronto’s starters have a 4.06 xFIP. Among AL clubs, that trails only the Twins (4.04) and their Jedi-like ability to avoid ball four.

Once a lukewarm prospect seemingly destined to be known as “not Troy Tulowitzki,” Ricky Romero is pitching like one of the better starters in the bigs. The 25-year-old lefty, taken with the 6th overall pick in the 2005 draft, owns a 3.14 xFIP on the season. Only Doc has a better mark among qualified big league starters. He’s punching out over a batter per inning (9.19 K/9), displaying decent control (3.38 BB/9) and burning worms (56.9 GB%). In 255.1 career innings, Romero has a 3.81 xFIP. It remains to be seen whether he can continue to pitch at an elite level, but at worst the Cal State Fullerton product looks like a comfortably above-average starter.

Shaun Marcum, returning from Tommy John surgery, has a 3.77 xFIP. The 28-year-old righty has whiffed 7.4 batters per nine frames, with 2.1 BB/9. A supplemental first-rounder in the 2007 draft, Brett Cecil is showing promise as well. Cecil was a strong ground ball pitcher in the minors (59.7 GB%, according to Minor League Splits). While that hasn’t carried over to the majors yet (42 GB%), the 23-year-old has a 4.02 xFIP in 2010, with 7.25 K/9 and 2.17 BB/9.

Romero, Marcum and Cecil have a few things in common. They rely heavily upon their secondary stuff, put fewer pitches in the strike zone than the big league average and garner plenty of swings on pitches thrown off the plate:

Romero supplements his 90-91 MPH fastball with a high-80’s cutter, a low-80’s slider, a low 70’s curve and a devastating mid-80’s changeup. Marcum’s 86-87 MPH “heat” is backed up by a mid-80’s cutter, a low-70’s curve and a low-80’s change. Cecil’s 89-90 MPH fastball is enhanced by a mid-80’s slider, a mid-70’s curve and a low-80’s change. On a per-pitch basis, this trio’s breaking and off-speed stuff has been stellar:

The changeup is a big pitch for all three — Romero (26.4 percent), Marcum (22.4 percent) and Cecil (24.6 percent) pull the string often.

Brandon Morrow shares the above trio’s tendency to put fewer pitches in the zone (45.2 percent) and induce lots of outside swings (31.3 percent), but he has gone to his 93-94 MPH fastball about 64 percent of the time. The former Cal star, who went back and forth between roles (starter? reliever?) with the M’s enough to make Hamlet groan, is now firmly a starter. The 25-year-old’s ERA (6.00) looks ghastly, but his xFIP (4.12) is much more palatable. Morrow’s control remains maddening (5.37 BB/9). However, he does have 10.42 K/9 and an 11.5 percent swinging strike rate (8-8.5 percent MLB average). It’s pretty hard to notice the positives when 35 percent of balls put in play are falling for hits, though.

ZiPS projects that the Jays’ top four starters will regress somewhat but continue to perform well for the rest of 2010 — a 4.23 FIP for Romero, 4.01 for Marcum, 4.38 for Cecil and 4.26 for Morrow (though that projection has him splitting time between the rotation and the ‘pen).

Marc Rzepczynski (4.29 preseason ZiPS) could contribute at some point after missing time with a broken finger. Jesse Litsch, another Tommy John survivor, is nearing a return. Dustin McGowan’s shoulder woes have derailed his career, though he’s still trying to work his way back. Halladay trade piece Drabek is performing well at Double-A. Zach Stewart (picked up in last year’s Scott Rolen deal) is scuffling at the same level, but he’s well-regarded, too. Luis Perez is a smallish lefty who gets plenty of grounders. Chad Jenkins and Henderson Alvarez show promise a little further down the minor league ladder.

It will be years before the Halladay deal can be fully evaluated. But happily, the Blue Jays have no shortage of promising young pitching talent within the organization.

Perhaps more than any other pitcher in the game, Joel Zumaya is associated with radar gun readings. After every fastball that the Detroit righty throws, flames literally shooting down his tattooed arms, fans turn to see if Zumaya cracked the triple digits.

The Tigers’ 11th round pick in the 2002 draft was developed as a starting pitcher, but he was shifted to the ‘pen upon reaching the majors. His rookie season back in 2006 was excellent — averaging 98.6 MPH with his vaunted fastball, Zumaya had 10.48 K/9, 4.54 BB/9 and a 3.93 xFIP. His control wasn’t great, but he garnered swinging strikes 13.4 percent of the time (9.3 percent MLB average for relievers) and compiled 1.9 WAR in 83.1 innings pitched. Zumaya’s heater wasn’t just a high-velocity novelty act — it was worth +1.43 runs per 100 pitches thrown.

After dominating hitters in ’06, Zumaya spent the better part of the next three seasons on the surgeon’s table or on the rehab trail. Joel’s injury woes actually began during the 2006 postseason, as he missed part of the ALCS with forearm and wrist inflammation suffered by rocking a little too hard on “Guitar Hero.” He then ruptured a tendon in his right middle finger in May of 2007, requiring surgery that sidelined him until August.

That off-season, Zumaya injured his shoulder moving boxes in his father’s attic as a California wildfire approached. He went under the knife again to repair his separated shoulder. Zumaya didn’t pitch in the majors until June of 2008, but he was shut down with a stress fracture in his shoulder in September. Last year, he began the season on the DL with shoulder soreness and then had yet another procedure on his shoulder in August.

When Zumaya did take the mound from 2007-2009, he wasn’t effective. He struck out 8.07 batters per nine frames, issued 6.24 BB/9 and had a 5.40 xFIP in 88 combined frames. After looking like a shut-down reliever during his rookie year, an ailing Zumaya contributed all of -0.2 WAR from ’07 to ’09. He still threw hard, averaging 97.5 MPH in 2007 and 2008 and 99.3 MPH in 2009, but hitters didn’t tremble at the prospect of getting a Zumaya fastball. The pitch had a +0.71 runs/100 value in ’07, but declined to -0.86 in ’08 and -0.94 last year.

In 2010, however, Zumaya again looks like a relief ace. In 26.2 innings, he has 9.79 K/9, 1.69 BB/9 and a 2.97 xFIP. With 1.1 WAR, the 25-year-old trails just Jonathan Broxton among relievers. Chucking his fastball (averaging 98.4 MPH) a career-high 84.2 percent of the time, Zumaya has a +2.48 runs/100 value with the heat. Joel is getting first pitch strikes 66.7 percent, and batters are chasing plenty of pitches — his outside swing percentage is 31.5, compared to a career 24.4 percent average and the 25.7 percent big league average for relievers.

I have no idea if Zumaya can remain healthy. Given his lengthy injury history and the stress that he puts on his shoulder with each searing fastball, he could be a ticking time bomb. But whatever the future holds, Zumaya’s pitching like one of the best relievers in the bigs right now.

Once a cherished prospect, ranked among the top 10 farm talents in the game by Baseball America before the 2002 season, Carlos Pena took a circuitous route to major league success. The 10th overall pick in the 1998 draft drifted through the Texas, Oakland and Detroit organizations, putting up full-season wOBAs in the .330s and .340’s — hardly standout marks for a first baseman.

Released by the Tigers in March of 2006, Pena toiled at the Triple-A level for the Yankees (who cut him loose in August) and the Red Sox. He inked a one-year, $800,000 minor league deal with Tampa Bay for 2007 and proceeded to post a .430 wOBA that season. The Rays rewarded Pena with a three-year, $24.125 million deal, buying out two years of arbitration and his first free agent year . Pena put up a .374 wOBA in both 2008 and 2009, but the free-agent-to-be is hardly having an ideal walk year in 2010.

In 189 plate appearances, the 32-year-old is batting .189/.307/.377, with a .304 wOBA. While his walk rate is still solid at 13.8 percent, it’s down from his 15-16 percent marks from 2007-2009. Pena had Isolated Power figures of .345 in ’07, .247 in ’08 and .310 in ’09, but his ISO sits at a comparatively mild .189 this year. To this point, he has been sub-replacement-level, with -0.1 WAR. What gives?

Over the ’07 to ’09 seasons, Pena showed quality plate discipline. He swung at a lower-than-average rate of pitches thrown outside of the strike zone — 19.8 percent in ’07, 20.8 in ’08 and 23.6 in ’09, while the MLB average was around 25 percent those years. Pena let it rip on in-zone pitches, with Z-Swing marks well above the big league norm, but he rarely got himself out on junk pitches off the plate.

This year, however, Pena has hacked at 31.5 percent of out-of-zone offerings (27.7 percent MLB average in 2010). It could be a coincidence, but perhaps pitchers have taken note of his uncharacteristic eagerness to chase. Opponents have put just 41.8 percent of pitches in the strike zone against Pena, compared to the 49-51 percent range from ’07 to ’09 and the 47.6 percent MLB average this season.

He’s making more (presumably weak) contact with those pitches out of the zone — 55.7 percent, compared to 42.5 percent in ’07, 48.7 percent in ’08 and 39.6 percent in ’09. The result of Pena’s expanded zone and higher out-of-zone contact rate is more 0-and-1 counts or balls put in play on the first pitch: his first pitch strike percentage is 64.6, way above his marks of 51.8 percent in ’07, 58.2 in ’08 and 55.1 in ’09 (58 percent MLB average).

Normally a prodigious pull hitter, Pena hasn’t lashed the ball to the right side with the same gusto this year:

He’s hitting fewer line drives, grounding out far more than usual and popping the ball up at a rate well above the big league average. The result is a .373 wOBA on pulled pitches, a far cry from his previous work and 26 points below the average for lefty batters.

Odds are, Carlos Pena won’t continue to hold a .214 BABIP and a wOBA that might get him confused with Ramiro Pena — Carlos’ rest-of-season ZiPS projection is .231/.354/.494, with a .371 wOBA. But clearly, he’s not helping his free agent stock right now. If Pena wants to get paid, he needs to show more restraint and start roping the ball to the pull field once again.

New York Yankees right-hander A.J. Burnett was rolling along last night against the Minnesota Twins, whiffing five batters, walking two and trading zeros with Scott Baker through five innings. And then, for the first time in the short history of Target Field, the rains came and delayed the action. The game was eventually suspended and will be picked up today.

Burnett pounded the zone with his fastball, tossing 35 of his 50 heaters for strikes (70 percent). But while Mother Nature threw a nasty curveball last night, Burnett missed the mark with his hammer — just 10 of 23 curves garnered a strike (43 percent).

According to our Pitch Type Values going back to the 2002 season, Burnett’s deuce has been one of the best offerings in the game. Per 100 pitches thrown, the low-80’s breaking pitch has been worth +1.6 runs above average. Over the 2007-2009 seasons, Burnett’s curve had runs/100 values of +2.03, +1.23 and +1.47, respectively. And he went to the pitch often. Never known for his changeup, Burnett used his curve 26.3 percent in ’07, 29.2 percent in ’08 and 31.1 percent last season.

In 2010, however, A.J. can’t seem to find his plus curveball. The pitch has a -0.14 runs/100 value. According to Pitch F/X data from texasleaguers.com, Burnett’s curve has been thrown for a strike only 47.9 percent of the time this year, compared to 56.4 percent in 2009 (the MLB average is about 58 percent). Batters have whiffed at 12.1 percent of curveballs thrown in 2010, a significant decline from last season’s 16.7 percent whiff rate (11.6 percent MLB average).

Not getting results with the curve, Burnett appears to have lost confidence in the pitch. He has thrown his breaking ball 23.5 percent of the time, preferring to go to his 93-94 MPH fastball on nearly three-quarters of his pitches. Burnett has typically tossed his fastball about two-thirds of the time, but his 2010 heater usage has few peers — among starting pitchers logging at least 50 innings pitched, Burnett trails only Colorado’s Aaron Cook and Seattle’s Doug Fister in fastball percentage.

Burnett’s four-seamer and sinker have been decent, with a combined run value right around the big league average. But those pitches don’t induce nearly as many swings and misses as breaking stuff. Burnett’s four-seamer has been whiffed at 6.4 percent (6 percent MLB average) and the sinker has a 5.2 whiff percentage (5.4 percent MLB average).

As a result, A.J. isn’t getting K’s like he usually does. Burnett has 6.39 K/9, his lowest mark since 2000 with the Marlins and nearly two punch outs per nine frames lower than his career average (8.3 K/9). The 33-year-old’s swinging strike rate is just seven percent, compared to the 8.3 percent MLB average and Burnett’s 10.2 percent mark since 2002. A.J.’s 83.2 percent contact rate sits well above the 80-81 percent big league average and his 76.5 percent clip dating back to ’02. Since inking a five-year, $82.5 million deal with the Yankees prior to 2009, Burnett hasn’t fooled batters near as much.

His 2010 xFIP (4.35) is similar to his 2009 mark (4.29), as Burnett has walked fewer batters and induced more ground balls compared to last season. But he isn’t pitching like the high-octane starter we came to know in Florida and Toronto. For A.J. to start getting more K’s, he’s going to have to rediscover his curveball.

Expected to finish no better than fourth place in the ultra-competitive American League East, the Toronto Blue Jays currently boast a 27-20 record, just a half-game behind the New York Yankees for second place in the division.

The Jays have gotten quality performances from both the rotation (4.15 xFIP, third in the AL) and the bullpen (4.00 xFIP, also third in the AL). But perhaps most surprisingly, Toronto leads the Junior circuit in runs scored, with 247. That total is due in part to timely hitting that almost certainly won’t persist — the Jays are batting .232/.289/.422 as a team with the bases empty, but have crushed to the tune of .268/.347/.537 with ducks on the pond. Based on the club’s .339 team weighted on-base average, Toronto’s offense should have churned out 228 runs so far — fourth in the AL.

So, the offense has been good, but fortunate to tally so many hits with runners on base. There’s another bizarre aspect to the Jays’ offensive attack this season, though — they’re swinging from the heels and making hard, loud contact.

As a whole, Toronto’s hitters have chased 31.1 percent of pitches thrown outside of the strike zone. That’s the highest mark in the AL and is well north of the 27.6 percent major league average in 2010. The Jays also lead the league in cuts taken on in-zone pitches, letting it rip 68.5 percent of the time a pitcher puts one over the plate (63.6 percent MLB average this season).

Taking such an aggressive approach, the Jays have the highest first pitch strike percentage in the AL — they have put the ball in play on the first pitch or gotten behind in the count 0-and-1 60.7 percent of the time (58.1 percent MLB average).

Not surprisingly, Toronto’s batters haven’t drawn many walks, with an 8.3 BB% that ranks 10th in the AL. But the team is outslugging the competition with a .221 Isolated Power. The Red Sox rank a distant second, at .183.

Hard-hitting hackers include SS Alex Gonzalez, C John Buck and CF Vernon Wells. Take a look at their respective career averages in O-Swing and Z-Swing (since 2002), compared to their swing percentages in 2010. Also included: their 2010 ISO figures, compared to their pre-season CHONE and ZiPS projections:

The MLB average for O-Swing percentage has increased in recent years, but even as a percentage of the big league average, 2010 ranks as the most hack-tastic season for Buck and Wells. Gonzalez chased an even higher proportion of pitches out of the zone (compared to the MLB average) during his Marlins days.

Though not to the same extent as the three guys above, Jose Bautista is chasing more pitches than usual (23.4 O-Swing percentage, 18.2 career average). And, as Dave Cameron noted, he’s hitting for unprecedented power — Bautista has a .325 ISO. Prior to 2010, CHONE forecasted a .163 ISO and ZiPS projected a .162 ISO. New Jay Fred Lewis has gotten into the act as well, with a 28.7 O-Swing (20.5 career average) and a .186 ISO (.142 pre-season ISO from CHONE, .153 from ZiPS).

Of course, not every Toronto hitter with a more aggressive approach is thriving in the power department. 2B Aaron Hill has a 32 O-Swing percentage (22.2 career average), but a .156 ISO (.171 pre-season CHONE, .172 ZiPS). Adam Lind showed improved plate discipline in 2009, but his O-Swing is back up to 30 and his .169 ISO falls short of his pre-season CHONE (.209) and ZiPS (.211) marks. Lyle Overbay has swung at 23.3 percent of out-of-zone pitches (18 percent career average), with a .143 ISO (.153 pre-season CHONE, .165 ZiPS).

Moving forward, Gonzalez, Buck and Wells figure to come back down to Earth. Bautista probably hasn’t suddenly become a gargantuan power hitter, but his 2010 start can’t be ignored. With better luck on balls put in play and perhaps a few less cuts at junk pitches, Hill, Lind and Overbay should rebound: