Danny Duffy: Simultaneously Unlucky, Lucky And Pretty Good

The introduction of sabermetrics into general baseball discussion over the past generation has brought the concepts of random chance and, dare I say, “luck” into the daily discourse surrounding the game. Hardcore opponents of analytics tend to deride the entire notion of luck, while analysts may too quickly ascribe variations in performance to random chance. The more factors we are able to quantify, the more easily we can decide what is random variation, and what isn’t.

Into this esoteric debate steps Royals’ lefthander Danny Duffy, who has posted a subpar 8-11 won-lost record – and a glittering 2.42 ERA, through his abbreviated one-pitch outing (due to shoulder soreness) on Saturday. And then that ERA is way out of whack with his fairly ordinary 3.68 FIP. Has he been as unlucky as his record tells us, or as lucky as his ERA might indicate? Let’s see what we can measure about both Duffy and the context surrounding him, to get a better feel for his true talent and the role random chance has played in his odd 2014 season.

Duffy has long been a top shelf prospect in the Royals system. He was a 3rd round draftee out of Cabrillo (CA) HS in 2007, and the competition he faced throughout the minors was the least of his worries. While always ranking as one of his level’s youngest pitchers, he compiled a gaudy 31-16, 2.88, career minor league record, with a 498/141 K/BB ratio in 425 innings. Obstacle #1 was a lapse in his passion for the game, as he briefly left the Royals in the spring of 2010, only to return a few months later, revitalized and ready to go. Obstacle #2 was Tommy John surgery in 2012, after a somewhat rocky major league debut the previous season. At present, it doesn’t appear that his current shoulder situation will represent obstacle #3 – he’s slated to just miss a start at this point.

Each season I compile an ordered list of minor league position player and pitching prospects, based both upon performance and age relative to the league. Duffy ranked among the top 40 minor league pitching prospects for four consecutive seasons, ranking #13 in 2008, #40 in 2009, #12 in 2010, and #4 in 2011. Guys who rank this high, this often, tend to be high-ceiling high school draftees. If they emerge from the injury nexus unscathed, they have a very high chance of experiencing significant major league success. After all of the bumps in the road along the way, 2014 was Duffy’s first extended chance to strut his stuff at the major league level.

At this stage of the game, pretty much everyone on both sides of the analytical divide would admit that the won-lost record statistic for starting pitchers is extremely limited in value. The 13-win Felix Hernandez Cy Young Award hopefully has settled that score. One hopes that no one is holding Duffy’s 8-11 record against him. Run support, as one might expect, has been a considerable factor, as the Royals have scored just 78 runs in his 23 starts, or 3.39 per game. That figure really doesn’t begin to tell the story, however. 48 of those 78 runs have been scored in just six of those starts, meaning that he has averaged a whopping 1.76 runs of support in his other 17 starts…..during which he has posted a 2-10, 2.40, mark. That my friends, is unlucky.

Why is there such a disconnect between Duffy’s ERA and FIP? Let’s review his 2014 plate appearance outcome frequency and production by BIP type data for some clues. First, the frequency information:

FREQ – 2014
Duffy % REL PCT
K 19.0% 94 26
BB 8.8% 114 82
POP 16.1% 209 99
FLY 29.8% 107 74
LD 18.5% 89 10
GB 35.6% 82 5

There’s some very telling information here. First, his K and BB rates are a bit lackluster – both are below MLB average with percentile ranks of 26 and 82, respectively. This puts the onus on Duffy to expertly manage batted-ball contact if he is to experience material success. And manage it he does. Take a gander at that massive popup rate, 16.1%, over twice the major league average, by far leading all ERA-qualifying starters in either league. In his previous major league appearances, Duffy had an above average popup rate, but nothing like this. This is the type of core contact management strength that a pitcher can build a strong career around – like Tim Hudson or A.J. Burnett‘s grounder rate, or before Duffy, Jered Weaver’s popup rate.

Weaver was one of those pitchers, going back to his amateur days, whose results were way better than his stuff. You’d grade him out as you would any prospect, and his overall grade would be much higher than the sum of its parts. He didn’t throw tremendously hard, didn’t have a plus-plus secondary offering, and though his command was very good, his mechanics were odd and made one wonder if they would hold up over time. Then you’d watch him pitch a couple of times, and notice that he’d flirt with double-digit popup totals each game. It wasn’t an accident. Hitters would pick up his fastball late, often up in the zone, and hit the ball straight up in the air. In 2009, Weaver had an incredible 18.3% popup rate, and in 2011, a 16.6% rate, the two highest of five straight seasons over 13.0%. This was and is the backbone of Weaver’s success. Popups are every bit as much a “free” out as a strikeout, and they emanate from talent, not from luck. Duffy, like Weaver, has a sneaky fastball which hitters pick up late, and often hit straight into the air when located up in the zone. His K rate might be ordinary, but his “free” out rate certainly is not.

Beyond the outlier popup rate, there is additional interesting info. His liner rate is very low, with a 10 percentile rank, but it is way too early in his career to determine whether this is a true skill, as it is for a minority of hurlers, or if it is ripe for upward regression. In his earlier cups of major league coffee, his liner rates were much higher. Like most extreme popup guys, Duffy possesses a fairly significant fly ball tendency (74 percentile rank), and an extremely low grounder rate (5 percentile rank). All of these fly balls mean that his overall performance will be heavily context-dependent. Let’s now take a look at the production by BIP type allowed by Duffy, both before and after adjustment for context, to get a better feel for the batted-ball authority he has allowed:

PROD – 2014
FLY 0.177 0.460 40 66
LD 0.529 0.757 69 102
GB 0.274 0.281 122 107
ALL BIP 0.245 0.372 56 75
ALL PA 0.191 0.266 0.291 65 82 2.42 2.44 3.07

The actual production allowed on each BIP type is indicated in the AVG and SLG columns, and is converted to run values and compared to MLB average in the REL PRD column. That figure is then adjusted for context, such as home park, team defense, luck, etc., in the ADJ PRD column. In the three right-most columns, his actual ERA, calculated component ERA based on actual production allowed, and “tru” ERA, which is adjusted for context, are all presented. For the purposes of this exercise, SH and SF are included as outs and HBP are excluded from the OBP calculation.

First of all, one had to expect some crazy numbers here, as Duffy has allowed all of 102 hits in 141 1/3 innings this season. His .245 AVG-.372 SLG on all balls in play is good for a 56 REL PRD, or unadjusted contact score. As a fly ball pitcher, the damage he allows in the air is key, and Duffy hasn’t allowed much. His .177 AVG-.460 SLG on fly balls is good for an off-the-charts low 40 REL PRD, which matches Matt Harvey’s major league low 2013 mark. Adjustment for context pumps that figure up to a 66 ADJ PRD. There’s room for credit all around here – to the ballpark, the outfield defense, and to Duffy.

Based on my own calculations utilizing granular batted ball data, Kauffman Stadium had a 70.0 fly ball park factor in 2013, the lowest in the majors, even lower than Safeco Field’s 71.8. If you’re a fly ball pitcher, this is the place to be. Then there’s the team defense. No matter which advanced metric you prefer, the Royals rank at or near the top of major league defenses, and their outfield leads the way – Alex Gordon, Lorenzo Cain and Jarrod Dyson are all clear plus defenders.

Then there’s Duffy. There are two ways to successfully limit damage on fly balls – to manage the vertical angle and the exit velocity off of the bat. Splitting the fly ball category into upper and lower groups equidistant in size from the popup and line drive borders yields starkly different results. The “higher” fly balls yield an .098 AVG-.234 SLG, while the “lower” ones yield a .380 AVG-.990 SLG. Roughly 35% of fly balls reside in the upper group, 65% in the lower. Duffy has allowed 47.8% “high” fly balls, and 52.2% “low” fly balls, an exceptional ratio that has made the outfield’s job easier and perhaps somewhat pumped up their advanced metric values.

Duffy has been extremely fortunate on line drives, with a 69 REL PRD figure that is pumped up all the way to just higher than MLB average (102 ADJ PRD). He has allowed over 30% less than average liner production despite allowing slightly higher than MLB average liner authority. The outfield defense certainly helps him out on this front as well. Duffy actually allows harder than MLB average contact on the ground, with his 122 REL PRD adjusted down to 107 for context.

His overall unadjusted contact score of 56 is adjusted upward to 75 for context – that figure will rank near the top of AL hurlers if he can squeeze out enough innings to qualify. Add backs the K’s and BB’s, and his actual ERA of 2.42 (65 REL PRD) is adjusted upward for context to a “tru” ERA of 3.07 (82 ADJ PRD). That is almost smack in the middle between his ERA and FIP. FIP simply does not give popup generators the proper credit for those outs are that are virtually as “free” as strikeouts.

Duffy is by no means assured material success going forward. Fully two-thirds of the pitches he throws are four-seam fastballs, and while he might be able to afford a drop of a tick from his average velocity of 93.3 MPH, a drop of a tick and a half might turn a bunch of the popups and “high” fly balls he allows into longballs. He also throws his curve – another fly ball-inducing, up in the zone out pitch – 21.1% of the time. There is a very fine line between excellence and obsolescence for starters with repertoires as narrow as Duffy’s. Weaver always had a third weapon – his changeup – to complement his fastball and curve, and was able to more easily retire hitters in all sectors of the zone. Duffy also needs to show the durability expected of a top-end starter – he has yet to record an out in the 8th inning of a major league game he has started.

Still, his ability to get free outs via a representative K rate and superior popup rate makes him a force to contend with in the intermediate term. The fact that he pitches his home games in arguably the most suitable park for his skill set, in front of an exceptional group of defenders, particularly in the outfield, raises his upside that much higher. Forget that won-lost record – Danny Duffy is way better than that, and his inflated FIP. He’s not as good as his ERA, but he’s plenty good enough.

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7 years ago

“Based on my own calculations utilizing granular batted ball data, Kauffman Stadium had a 70.0 fly ball park factor in 2013”

Is this secret sauce, or can you divulge the method you use to compute that?

Great article nonetheless