Zack Greinke is a really good pitcher. That’s why he signed a monstrous $200+M deal in Arizona before the 2016 season. Unfortunately for Zack Greinke and the Arizona Diamondbacks, he wasn’t really good during the 2016 season.
Something went wrong in the desert. Part of it could have been that Greinke was pressing, trying to live up to his big contract and the largest per-year salary in baseball history. Part of it could have been adjusting to a more hitter-friendly home park (he had a 4.81 ERA at home versus a 3.94 mark on the road in 2016 with FIP and xFIP showing similar spreads). Whatever his issues were, the Diamondbacks and their fans were hoping for more out of their expensive ace in 2017.
Through seven starts, the results have been encouraging. He has pitched to a 3.09 ERA (and a 3.15 FIP/3.05 xFIP) despite his GB% and HR/FB% remaining the same as 2016. One thing that has changed is that he’s allowing 30% fewer walks while striking out two more batters per nine innings. Another thing that has changed is that he’s throwing his slider more than ever before.
After his most recent start, a win at Colorado on May 5 where he threw seven innings and allowed two earned runs, Greinke was asked about his slider usage in the game. He replied:
“I threw a decent amount, I don’t know how much more than normal, against righties, but, it was working. Could have thrown more, might have had better results, it was just working really good. I throw it more to righties and they had a lot of righties in their lineup today.”
In fact, he threw a higher percentage of sliders than in any other start in his career, and the highest since 2011. According to Brooks Baseball, in 2017 he’s thrown a higher percentage of sliders than in any other year in his career (25.7%). In terms of raw pitch counts, he threw more sliders in April (144) than in all but two other months in his career. He is throwing more sliders than normal.
He was right about one thing, though: the pitch is working. Facing the Rockies at Coors, Greinke threw 38 sliders with a 26.3% whiff rate while only allowing one hit. So far in 2017, he’s getting a 26.1% whiff rate with his slider after only getting 21.5% in the last two years. He’s also getting the highest Swing% of his career, and had his second-highest month of raw whiff counts in April.
So what has changed about the pitch besides its usage?
He is not throwing it as hard as in recent years, while also seeing an increase in horizontal movement. Brooks Baseball has his slider velocity at its lowest and his horizontal movement at its highest since 2013.* Additionally, he is locating the pitch closer to the plate than he has in years, while maintaining the same height in the zone. He is also getting a higher percentage of called strikes this year than in 2015 or 2016, years in which his horizontal location moved away from the plate.
It is not a completely new pitch, but it has changed, and he is using it differently. Located closer to the plate, and moving more, the pitch is getting more swings and calls, leading to more strikeouts and fewer walks. There is little wonder that he has thrown it as much as he has.
*I omitted his Colorado results because as we know, Coors suppresses movement. If you look up his Brooks Baseball movement chart you will see a massive dip in horizontal movement for May 2017 as we only have the Coors start to draw data from.