Q&A: Glen Perkins, A Twin, His FIP, and Math

Glen Perkins knows his FIP. He also knows his HR/9, Z-Swing% and O-Swing%. More importantly, he understands what they mean. As the Minnesota Twins left-hander says, “I like baseball and I like math.”

Perkins is more than a stat geek. The 30-year-old converted starter is one of the better closers in the American League (despite his skepticism of modern-day closer usage). Six weeks into the current campaign he’s well on his way to topping last year’s save total, despite a markedly higher ERA — a number he considers less important than his FIP.

Perkins talked about his 2013 numbers prior to last night’s game at Fenway Park.


Perkins on knowing the numbers: “In 2010, when I was in Triple-A, I came across a FanGraphs story about Brandon McCarthy and how he was changing his pitching style to get more ground balls and maximize his abilities. From there I started reading more and more. I’ve always been a math guy and the two sort of go hand-in-hand. I like baseball and I like math.

“In 2008, I thought I’d had a good year. I won 12 games and had a 4.40 ERA. That wasn’t great, but I was like, ‘that’s not bad.’ But the more I read, the more I came to realize it’s not about wins. It’s about the quality of the innings you pitch, and my quality wasn’t that good.

“In 2009, I started out the season with three eight-inning starts and only gave up three runs total. But I only struck out 10 guys in the 24 innings. I read somewhere that I was going to regress. I thought ‘What?’ It didn’t make sense to me. That’s when I began poking into it, but I mostly brushed it aside. Then, in 2010, I started reading more and more. I began to realize wins were a result of quality innings, not the barometer of how good you are.”

On what he considers the most important pitching stat: “Fielding Independent Pitching [FIP]. That’s what a pitcher can control, and the lower it is — just by default — the lower your ERA is going to be over the course of time. Not walking guys, getting strikeouts and ground balls, and not giving up home runs, are the keys. I don’t ever want to walk a guy and would strike everyone out if I could. If I can’t strike them out, I’d like to jam them so they hit a pop up to the infield, or a ground ball.”

On if his 13.5 K/9 is sustainable:
 “The last two years it went up. My swinging-strike rate has gone up. I know my chase-rate is down, but my in-zone swing-and-misses are higher this year than last year. Obviously it’s a small sample.

“So, I don’t know. I’d like to think so. I don’t know if there’s a stat for an expected strikeout rate based on swings-and-misses and chases. I guess maybe where I’m at is a little high, but I think I can improve from last year when I was at 10 per nine.”

On his O-Swing% [38.9] and Z-Swing% [71.4]: “I typically know what gets swung at — it’s usually fastballs up and out of the zone, and sliders below the zone. Having a higher O-Swing rate obviously means they’re chasing pitches, but it also means they don’t know what’s coming — or they can’t react. That’s a good indicator of how much chance a hitter has. Getting big-league hitters to swing at pitches out of the zone is hard to do. Getting big-league hitters to swing and miss at pitches in the strike is even harder. But you can make quality pitches in the strike zone, and I feel my stuff allows me to pitch in the strike zone.”

On his F-Strike% [74.4]: “It’s a known fact that a guy hitting 0-1 is significantly worse than a guy hitting 1-0. Getting to 0-1 is also the quickest way to 0-2. At 0-2, a hitter has a very small chance and that chance is probably a single. But you can’t just throw it down the middle of the plate. For me, getting to 0-1 is just as likely to be a competitive slider down in the zone, or even below the zone.

“In most of the situations I’ve pitched in this year, we’ve been leading. Guys are typically taking a pitch in that situation — I’ve known they might be giving me that first pitch — but even so, you never throw a ball down the middle. I might throw a four-seamer in or I might throw a slider.”

On his BB/9 [3.38]: “I think my walk rate right now is mostly based on small sample size. I did this last year. I had a game against the A’s where I walked three guys in one inning, and outside of that I only walked 12 or 13 guys all year. This year, two of my five walks came in one game against the Rangers. Good command is the last thing to come. As the season goes on, I get more comfortable with my delivery.”

On his GB% [26.1]: “There’s a small sample size there as well, but so far this year I’ve struggled with extension. As a result, I haven’t had as much downward action on my ball. But I pitch more with four-seamers now, and… I don’t know what the swing rate is on my slider, but I would imagine that’s my main ground-ball pitch. I haven’t gotten a whole lot of balls in play on my slider.

“The two-seamers haven’t been there. I didn’t throw a lot of them last year. From 2011 to 2012, the usage of those two kind of flip-flopped. My four-seamer comes in harder, so I’m throwing more of those.”

On his HR/9 [0.84] and HR/FB [10.0]:
“In 2011, I only gave up two home runs. I got a ton of ground balls — it was just under 50 percent — and last year my fly-ball percentage and home-run percentages went up. I think I was right around league average on home-runs-per-fly ball. I would assume that this year, at whatever point that stabilizes, I’ll be around 10 or 11 percent. That’s why I’d like to get more ground balls.

Greg Maddux said to me at the World Baseball Classic this year, ‘If you get your balls hit in front of the outfielders, you did your job.’ Some balls are going to fall in and there are going to be line drives hit right at guys. It’s about not letting the ball go over the fence.”

On his ERA [4.22] and FIP [2.34]: “My [current] ERA isn’t a concern to me. My main concern is what I’ve done in the seven games where I’ve come in and gotten a save. I’ve given up something like four hits and one run and struck out 13 or 14 guys, in those seven games.

“In one game we lost 16-5 [to the Mets] and I gave up two runs. In another game we lost 7-2 to the Rangers and I gave up two. Outside of that, I’ve given up one run. As time goes on, my ERA is going to get closer to my FIP. The more I minimize home runs, the lower my ERA is going to get.”

On being 7-for-7 in save opportunities: “Do I particularly agree with closers in baseball? That’s a tough question that I ask myself. But it’s my job, and when I go out there to do that job, saves are the most important thing to me. If I throw a quality inning, that’s the result I should get.”

David Laurila grew up in Michigan's Upper Peninsula and now writes about baseball from his home in Cambridge, Mass. He authored the Prospectus Q&A series at Baseball Prospectus from December 2006-May 2011 before being claimed off waivers by FanGraphs. He can be followed on Twitter @DavidLaurilaQA.

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10 years ago

This was an awesome article. I love these player interviews.