What’s Up With Greinke’s Slider?

Zack Greinke goes to the mound today after giving up 13 runs in his last three starts, something he didn’t do at all last year. So we’re all trying to diagnose him. He is, too. We couldn’t figure it out together, really. Sorry to spoil the ending.

The slider is getting hit hard. Of his pitch types, it has the second-worst exit velocity so far this year, and it’s suffered the most from last year to this year.

So something is amiss with the slider. Greinke admitted as much. “The first game, the slider was bad,” he told me before Tuesday night’s game against the Giants. “It was not good. The last two games, the slider has been closer to normal. It had no bite to it at all in the first game. The last game, it was pretty sharp. I still threw some back-up ones.”

A traditional look at his slider movement doesn’t produce a ton.

Yes, he’s gotten more side-to-side movement on his slider as the season has progressed, and it’s gotten the tiniest bit harder. But! It’s become less like his average slider from last year. It’s a bit more horizontal this year.

Let’s try another look, with the newer numbers at our disposal. Here are Greinke’s spin rates on his pitches last year and this year. See if you can spot the outlier.

Maybe his slider spin is off. Maybe it was just a few back-up sliders, though. Not every slider registers a spin rate, and this sample isn’t huge to begin with. We return to Greinke’s words. “I’m not throwing that good. Inconsistent. Last game I still threw some back-up sliders. Not something you want to do a lot. Just not quite there.” And he shrugged off any chance that offseason work was the reason. He “might have done a little less throwing than usual” but he should be fine soon.

For some reason, though, people aren’t swinging at his slider as much this year. You’d think, if it were bad, they’d swing at it more. But right-handers swung at 59% of his sliders last year, and that’s down to 53%, the biggest change in swing rates on any of his pitches.

Perhaps it’s location. “I’m throwing one more pitch middle-middle per game, which I guess is a lot but it shouldn’t make a big difference,” Greinke said. “The location hasn’t been as good, it just hasn’t.” This is how you can be bad with a pitch and still get fewer swings — Greinke’s misses with the slider are worse this year. His average location for a righty on righty slider has moved three inches downward, and that’s important. His average slider used to miss the outside corner down off the plate by 2.9 inches; this year it’s been missing by 6.3 inches. It’s easier to take a slider that’s low by a half a foot than one that’s just a few inches off the bottom of the strike zone.

In any case, batters are hitting him harder this year. Last year, he was 23rd in average exit velocity, and this year he’s 39th, and Russell Carleton just found that pitchers’ exit velocities stabilize after 50 balls in play… sort of. Greinke’s had 54 balls in play, and was a bit paranoid about his exit velocity given his results. His actual ranking reassured him. “There’s still work to do,” said Greinke, “but that made me feel better.”

Carleton also found that adding more data did not lead to better correlations for pitchers exit velocities past and future. The idea is that pitchers’ can affect their performance drastically from start to start and change their true talent, in effect. And that’s what Greinke is hoping to do. The park is “obviously tougher” but a little work on his slider location and bite, and he should be back to normal.