Counting on Corbin

Patrick Corbin has been a regular topic of thought and conversation for me the past few weeks, which tells you one thing about me – that I maybe think and talk about baseball more than I should – and another about him – that there is considerable reason to discuss him. Both are true.

First, Brad Johnson projected a wide range of values for Corbin and offered his expectation that Corbin would fall near the bottom of that range. Then, I had a long (for Twitter) conversation about him on Twitter. Michael Salfino asked why Corbin was so underrated; I suggested that his K/9 might be the problem, Eno Sarris pointed out a scary platoon split, and now I am here to tell you not to be worried about either.

The low K/9 is a problem he has had since Rookie ball, but he has shown flashes of much better numbers. In his first taste of High-A, he K’ed more than a batter per inning, and he did the same in his one brief stint in Triple-A. Other than that, the strike out numbers have been less than impressive, including 7.53 K/9 in 315.1 MLB innings.

What makes this so odd is that in 2013, Corbin posted a 10.7% SwStr%, 12th highest among qualified MLB pitchers. The other guys between 10th and 15th (Chris Sale, Homer Bailey, Felix Hernandez, A.J. Burnett, and Stephen Strasburg) posted the following K/9: 9.49, 8.57, 9.51, 9.85, and 9.39. Corbin’s 7.69 certainly looks like an outlier.

Corbin also led the league in F-Strike%, getting in front of hitters an astounding 70.2% of the time. Cliff Lee also cracked 70% with a 71.6% rate in 2012, but before that you have to go back to 2006 (Mike Mussina) to find another pitcher getting ahead that often. You probably know that starting 0-1 vs. 1-0 makes a huge difference, but what you may not know (at least I didn’t until I checked) is that F-Strike% correlates highly year-to-year. Looking at pitcher plate discipline data dating back to 2009 (five seasons), F-Strike% in a given season has a correlation of .64 to the pitcher’s F-Strike% in the previous season. In fact, all of the pitcher plate discipline stats correlate at .60 or better. So when you see that a guy like Corbin is creating a lot of swinging strikes or getting ahead of guys or inducing guys to chase an awful lot (8th in O-Swing%) you have good reason to think he will do that again.

So the guy gets ahead of hitters, induces swings on bad pitches, and has an elite SwStr% – and yet he strikes out only about 20% of the batters he faces. At least to my eye, when you start projecting Corbin for 2014, you either need to believe his plate discipline stats will fall off (he’ll start fewer guys with strikes and induce fewer swings and misses) or you should expect to see the K/9 climb.

So what about Eno’s concern about the platoon split? Well, Corbin certainly struggled with righties, at least compared to lefties. His FIP against fellow left-handers was 2.14. Against right-handed hitters, it was 3.81. It’s worth keeping in mind, though, that 3.81 – while not good – is not a bad split. Only 15 left-handed SP had a better FIP against righties last season. Not impressive, but not a disaster.

His issue actually seems to be an inability to strikeout right-handed batters. Lefties had a higher LD% and HR/FB rate against him (although they hit far fewer fly balls, which led to far fewer HR) and were more likely to pop the ball up. They even walked less often (6.1% vs. 7.0% of lefties). But while Corbin K’d 33.2% of lefties, only about half that many righties (17.2%) struck out.

This pattern goes back to 2012. In his first taste of MLB competition, Corbin again struck out 17.2% of righties (vs. 26.1% of lefties), while giving up more fly balls and, as a result, more home runs.

But 2013 actually showed a lot of progress in his platoon split. In 2012, Corbin faced 366 right-handed batters and they tattooed him to the tune of a .265/.313/.470 line with a .290 BABIP (lefties actually posted a better line, but a .441 BABIP makes those numbers pretty easy to ignore for now). In 2013, the line was .247/.305/.398 with a .281 BABIP. Basically, every right-handed batter he faced in 2012 was like a less whiff-y Pedro Alvarez (.244/.317/.467 that year); in 2013, they were more like Andrelton Simmons (.248/.296/.396).

That was not the only change from 2012 to 2013. That elite SwStr% was new (up 2 percentage points from 2012), as was the first-pitch dominance (up 11.6 percentage points). The reason underlying all these improvements seems to be a shift in pitch selection.

In 2012, he threw 30% four-seamers and 38.9% two-seamers, despite the fact that the former was not impressive (1.38 runs below average per 100 pitches for his career) while the latter was (.84 runs above average per 100 pitches). In 2013, he threw 51% two-seamers and only 16.6% four-seamers.

He also increased his slider usage (from 16.7% to 22.8%) while relying less on the change (13.7% to 9.6%). The change is his worst pitch (2.08 runs below average per 100) while the slider is his best (1.30 runs above average per 100). Among those pitches, only the slider showed significant improvement (statistically) year-over-year, going from .93 runs above average per 100 to 1.43 runs above average per 100.

Basically, the guy went from throwing his two worst pitches 43.7% of the time to throwing them 26.2% of the time.

All in all, I see no reason to think that Corbin can’t repeat what he did in 2013, and there are good reasons to be bullish about his K%. If that goes up, it not only eliminates the weakest part of his fantasy game, it has the potential to make all the other numbers (ERA, WHIP) better as well.

I am buying Corbin. Early in the year, I’ll be tracking his pitch usage, his ability to get in front of hitters, and his SwStr%. I see no reason to expect any of those to change, and if that is the case, I’ll be very happy to have this undervalued asset on as many rosters as possible.

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Chad Young is a product manager at Amazon by day and a baseball writer (RotoGraphs, Let's Go Tribe), sports fan and digital enthusiast at all times. Follow him on Twitter @chadyoung.

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Good stuff, but isn’t all this pretty easily explained by the slider? That pitch is truly elite, hence the SwStr%, but he can’t throw it all the time and isn’t keen on throwing it to right-handers. That narrative fits with the platoon split and the SwStr%/K% discrepancy. Unless he continues to up his slider usage, and therefore presumably elevates his injury risk, he’s probably not going to increase his K-rate. The slider is an out-pitch, while the fastball is pitch to contact.