Since his arrival in the big leagues, the best way to describe Luke Gregerson is simply “unhittable.” Last season, Gregerson posted a 3.24 ERA/2.50 FIP/3.11 xFIP in seventy-five innings with a K/9 of a whopping 11.16. This year, he’s walking two batters less per nine innings, and with some BABIP help is down to a line of 2.66 ERA/2.43 FIP/2.60 xFIP. However, he’s also decreased his tERA from 2.56 to 2.13. The groundballs are down while the flyballs have increased, which isn’t usually a good sign, but it is partially due to the decrease in line drives (which is most likely going to regress a bit). Gregerson has also begun to throw his slider a bunch more this year, up to 61.4% from 49.6% last season. Joe Pawlikowski wrote about about Gregerson’s nasty slider in early June:
The Padres’ bullpen has benefitted greatly from Gregerson and his slider. The unit claims the NL trifecta of fewest walks, most strikeouts, and lowest batting average against. They’re getting help from everywhere, but Gregerson has been a particular bright spot this season. The high slider frequency does cause a little concern, but for right now it’s his nearly unhittable weapon. I can’t imagine being an opposing hitter and standing in to face him.
Using the Bloomberg Sports Pro Tool, I wanted to take a closer look at Gregerson’s slider:
The top image shows all sliders thrown by Gregerson in 2010 to right-handed batters, while the bottom image shows the batted ball location of all those pitches. The highlighted balls in the top image correspond to the highlighted balls in play in the bottom image. As you can see, when Gregerson leaves his slider up and in/over the plate to right-handed hitters, it tends to get hit relatively far compared to all of his balls in play. Still, there’s only one homer there and a bunch of flyouts and a few groundouts, so even Gregerson’s hung slider isn’t all that bad. Here are the pitches from the lower-right quadrant of the batter’s box:
When Gregerson is able to locate his slider, batters don’t stand a chance. This also only includes batted balls. Look at Gregerson’s swings-and-misses generated by his sliders versus righties in 2010:
Gregerson’s slider has been worth 12 runs above average this season (from our own numbers here at Fangraphs) after an outstanding 18.7 mark last year. You can see why.