Randy Choate, Platoon Splits, and Arm Slots

It was the inning that shouldn’t have been.

First, in the tenth inning of Game Three of the National League Championship series, the Giants saw Brandon Crawford stroll to the plate against Randy Choate. It’s easy to say that the matchup didn’t favor the hitter based on Choate’s career splits. Choate has struck out 27% of the lefties he’s seen, and only walked 7.7%. Crawford walks 8.7% of the time against lefties, but his strikeout rate jumps to 24.5% when he’s seeing a southpaw.

Since both the expected strikeout rates were above average, you’d expect a multiplier effect. In other words: a lefty at the plate that’s particularly bad against lefties is even worse against a lefty that is particular hard on lefties. If you want to know more about this phenomenon, check out Steve Staude’s excellent post. If you want a table summary, check out this expected strikeout rate for a plate appearance based on the pitcher and batter’s respective strikeout rates:

		Pitcher’s K%
		10%	15%	20%	25%
Batter’s K%	10%	5.3%	7.8%	12.0%	14.6%
	15%	8.1%	11.4%	16.0%	20.8%
	20%	11.8%	15.6%	20.6%	26.9%
	25%	13.6%	21.0%	24.6%	34.9%

Maybe we could have expected Brandon Crawford to strike out in about 35% of those at-bats. Or 31.3% if you use the calculator in the piece linked above. Add in the fact that Choate has allowed a .254 batting average on balls in play against lefties, and you realize that Crawford’s expected on-base percentage for that at-bat was probably around .200.

He wasn’t expected to do much against an arm slot like that — he admitted that it’s “hard to get comfortable with that arm slot — he’s almost coming from behind you.” Jeremy Greenhouse once represented platoon splits by arm slot, and you can see that where Choate releases the ball is particularly tough on lefties. (I’ve added the annotation.)

So yeah, the deck was stacked against Crawford. But at least he’d seen him before. As Crawford put it, “I’ve faced him a decent amount of times… not a whole lot of success, but I’ve actually been able to draw a few walks.” In ten plate appearances, Crawford has drawn four walks. Given the tiny sample, it’s not enough to move the statistical needle, but at least Crawford had some familiarity.

When the advantage swung around the other way, in the next at bat, it didn’t even seem like we’d ever get to see a true outcome between Juan Perez and Randy Choate. The bunt sign was on, as the home team was playing for one run and one run alone.

But it was the complete unfamiliarity that Perez had with the arm slot that ended up helping us to a non-bunt outcome. As Perez said after the game, he’d “never seen someone with a release point like that, where the ball is almost coming underhanded.” He’d certainly never bunted off of someone like that.

“After I failed at my job, I just wanted to make sure I hit the ball hard somewhere,” said. Perez. Now the math was in his favor. Now, given their respective strikeout rates against the hands at the plate, the expected strikeout rate for that plate appearance was 13.3%. Now, Perez had seen the ball twice from that arm slot, and now the batter was in the green.

After a foul and another ball, Choate had thrown 13 pitches. Not one had been a slider. Sinkers have the worst traditional platoon splits in baseball. Choate tried to throw an inside sinker and this is where it ended up.

Perez was ready for it. He had considered going the other way on the fifth pitch, on the outside, but when it was a ball, he recalculated. “I reminded myself he had a good sinker, so I choked up and looked to pull the ball,” he said after the game.

Maybe those ten plate appearances against Randy Choate prepared Brandon Crawford enough to beat the numbers stacked against him. Maybe those two failed bunt attempts prepared Juan Perez enough to pull the ball into left field and set the table for the end of the game. Those things we can’t know for certain.

Should the Giants have subbed a righty like Joaquin Arias in for Brandon Crawford? Should they have let Juan Perez hit away from the start? Should the Cardinals have taken Randy Choate out against a righty once a batter was on? Those answers seem a little more certain.

What we definitely know, though, is that Choate’s arm slot made a big difference in Tuesday night’s outcome. Even if there were things that shouldn’t have been.