Originally written on Fangraphs  |  Last updated 9/23/14
You’re going to be reading a lot about Matt Garza, if you haven’t already. This being July, it’s officially trading season, and Garza is probably the best starting pitcher on the market. So, rumors. Let me try to distill what I’ve seen: there’s talk the Cubs might reverse course and sign Garza to a long-term extension, but that probably won’t happen, and Garza will probably be dealt, probably soon. The free-agent-to-be has been scouted by just about everyone with an interest in pitching, because scouting is cheap. Garza’s going to be in demand, and he’s allowed five runs over his last five starts. Among his opponents over that five-start stretch: the Astros, the Mets, and the White Sox. The Cubs would like to pitch Garza as a top-of-the-rotation ace, but that’s not the right label. By ERA-, he’s been as good as Mat Latos, but by FIP- he matches Scott Feldman, and by xFIP- he matches Yovani Gallardo. Over the rest of the season, ZiPS projects Garza to pitch similarly to Ricky Nolasco and Edwin Jackson. This has all been Matt Garza in a nutshell: he’s a good pitcher and an available pitcher, but he’s a three-month pitcher who isn’t worth torching the farm. He’s unlikely to be a guy who saves a season. But if you’re interested in Garza’s future, you might be interested in Garza’s performance record. And if you’re interested in Garza’s performance record, you might note something about his platoon splits. I’m going to warn you, this might get kind of gory, but these days, rumors are boring. Analysis is where the magic is, and if you want to better understand Matt Garza, you should understand that he’s a starting pitcher with an established reverse platoon split. This doesn’t change anything about his overall performance. Overall, Garza is something like a classic No. 2, who has flashes of ace-hood. He’s set himself some pretty consistent whiff and walk baselines. But the color’s in the details, and having a reverse platoon split is unusual. That’s why the word “reverse” is in there, to indicate weirdness. This season, Garza’s struck out a quarter of lefties and a fifth of righties. Lefties have flailed to a .270 wOBA; righties have flailed a little less, to a .300 wOBA. But that’s one part of one year. Over Garza’s career, spanning more than a thousand innings, he’s whiffed more lefties and allowed a slightly lower wOBA. It’s not just that the wOBAs are less than even — it’s that they’re not lopsided in the ordinary way. Garza gets things done differently. Since 2008, 248 right-handed pitchers have thrown at least 100 innings against both righties and lefties. Of those, 98 have a reverse split in terms of strikeouts. 69 have a reverse split in terms of FIP. 49 have a reverse split in terms of xFIP. 66 have a reverse split in terms of wOBA. Just 24 pitchers have all four, Garza being among them. His peers run the spectrum from Lance Cormier to Jered Weaver and James Shields. Being in this group doesn’t make Garza particularly good or particularly bad — it just makes him odd. When people observe something odd, they look for explanations, and when we see a reverse platoon split, we usually assume it has to do with the pitcher having a quality changeup or cutter. That’s why Shields is in that group. David Robertson’s in that group because of his deception and dynamite curveball. Garza throws a curveball, but he doesn’t really throw a cutter or a change, and he throws a bunch of sliders, even to lefties. Sliders are supposed to have a big and normal platoon split. So what gives, as far as Garza’s concerned? A National League hitter who’s faced Garza pointed to the movement on his slider. Garza’s slider, it was said, moves mostly up and down, with late break and minimal horizontal tail. The downward break makes things more difficult for lefties to see and square up. When asked for a comparable slider, the hitter mentioned Matt Harvey, who might well start next week’s All-Star Game. Harvey’s slider moves in a similar way, and Harvey, like Garza, shows a reverse platoon split, striking out a bunch more lefties than righties. Below, you’re going to see three sliders. One is a Garza slider, one is a Harvey slider, and one is a Jhoulys Chacin slider, chosen because Chacin’s slider has a lot more horizontal movement to it. That’s the stuff that gives the average slider its average platoon split. That’s the stuff that Garza and Harvey’s sliders are lacking. According to PITCHf/x, Garza’s slider has about an inch of horizontal movement. Harvey’s slider is the same in that way. Chacin’s slider, meanwhile, comes in at a little over eight inches. A glance at the Baseball Prospectus PITCHf/x leaderboards shows that Garza and Harvey have sliders near the bottom of the list in terms of horizontal movement. Or near the top of the list, if you sort the list in the opposite way. Because of the way those sliders move, you can see them as being either less effective against righties, or more effective against lefties. Or both, because it’s probably both. Over Garza’s PITCHf/x career, righties have slugged .311 against his slider, while lefties have slugged .301. Lefties have posted a comparable whiff rate. Over Chacin’s career, righties have slugged .282 against his slider, while lefties have slugged .381. There’s a substantial difference in whiffs. This year, more than half of Garza’s strikeouts of lefties have come on his slider, and he’s thrown the pitch 41% of the time in two-strike counts. That’s something that’s developed over time: Garza against lefties in two-strike counts: 2008: 20% sliders 2009: 25% 2010: 20% 2011: 37% 2012: 36% 2013: 41% Matt Garza is a right-handed starting pitcher who throws a lot of sliders to left-handed hitters. Matt Garza is a right-handed starting pitcher with an established reverse platoon split. Lefties see more sliders than curveballs, and they almost never see a change. In fairness, it’s not all about Garza’s slider. His four-seam fastball has been a real weapon against lefties, which is a factor in its own right. Maybe it deserves its own due. But it’s rare that a guy throws a slider that works against opposite-handed hitters, and from this we can learn about Garza, and about sliders and platoon splits. Our understanding of how these things work is probably too simplistic. None of this changes the fact that Garza is good without being great. He just gets to his own performance level by an unusual route. Maybe Garza could stand to be better when he pitches against righties. But as a righty, he faces a lot of lefties, and there he can’t be exploited.
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