If a pitcher wants to lose their spot in a rotation, a good way to do so is to struggle against one of either right or left-handed batters. Which pitchers had such problems in 2013?
Looking only at pitchers who qualified versus both lefties and righties this past year, we're left with a group of 60. Notable omissions, those who didn't qualify against one side of the splits, include names like Clayton Kershaw and David Price, which is likely due in part to teams shying away from running same-handed hitters at pitchers. That is unfortunate for the purposes of this study, because I would imagine that those types of pitchers that were platooned against would show the greatest splits. I'm going to roll ahead anyways, as cutting down the minimum qualifying standard would just cut down on an already small sample size.
Here is the chart that shows stats against right-handed batters subtracted by stats versus lefties. For example, a K/9 of 7 vs righties subtracted by a a K/9 of 5 vs left-handed batters would result in a difference of 2. Hooray for simple math! It is noteworthy that I colour-formatted the xFIP split column in the chart, but the colours are more for decoration and easily spotting big split stats. A green-filled box is not better than an orange-filled one; but rather just shows which handedness they struggled with. For example, Lance Lynn has a major platoon split, as his xFIP is roughly 2 runs higher against lefties; the corresponding box is filled orange-ish to highlight the split. CC Sabathia struggled to a similar degree against righties, but his is shaded green. It is alphabetical by first name. I split it into two pictures; this was a struggle, mostly since I am generally incompetent when it comes to interwebs.
Cool. Lance Lynn had the biggest xFIP split, as it was 1.86 higher against lefties than righties. Others who struggled against lefties (relative to how they performed against right-handers) were, in order, AJ Burnett, Rick Porcello, Kris Medlen, and Bartolo Colon to round out the five most extreme. At the opposite end of the spectrum (those who struggled most against right-handed batters) is CC Sabathia, CJ Wilson, Mike Minor, Ubaldo Jiminez, and Cole Hamels, in that order. It seems noteworthy that the only reverse-split (ie; better against same-handed hitters) was Jiminez. This is pretty informative, I think, as a pitcher like Lynn may not be long for the rotation if he simply can't get through left-handed opponents. On the other hand, if he improves against lefties, he could quickly become a top-of-the-rotation guy.
Ubaldo Jiminez would be the odd case, wouldn't he? Lets look at his career and see if this is a theme throughout the years. As it turns out, his xFIP vs R is 3.88 while 4.04 v L; much closer to what you would expect from a right-hander. While Jiminez didn't regain any velocity or anything magical like that, he did tinker with his pitch usage, as he upped his slider offering rate about 8%, while throwing his curve just 3.7%, down from his usual 8-10%. Lots of things happened with Jiminez last year, and if you want to dig further, please do. In any case, his new reverse-split may be something to keep an eye on going forward.
How do other pitchers on the list, and their 2013 splits, compare to those of their careers? To find out, I simply took their 2013 xFIP splits, and subtracted that from their career xFIP splits. The result should highlight any changes in an effective way. Intuitively, Jiminez should show up as one of the major differences from 2013 vs career splits. Here is the now entirely colour-formatted chart. Hopefully this makes sense from first glance. My apologies if it fails miserably.
The biggest overall changes in splits from this past year relative to the players' career were courtesy of AJ Burnett, Ubaldo Jiminez, and Cliff Lee. They all saw at least a full run change in their xFIP splits last year. Like Jiminez, both Lee and Burnett have historically had pretty neutral split stats. A next-step in this research would be to try and discern why the changes in their splits occurred, and if any trends emerge.
So anyways, that should satiate your need for split stat analysis for today. The gaps in xFIP here also provide some guideline numbers to use when looking at those not on my charts. If you see a starter with an xFIP split greater than 1.86, write Lance Lynn a letter and let him know that everything is okay. I'm also going to keep an eye on some of these guys to see if they regress back to their career norms, or if they actually developed a platoon split. It happens, y'all.
Thanks for reading.