One of the bigger pre-season storylines this year was the numerous relievers who were being used in their respective rotations. A number of them struggled, but a few have exceeded expectations. Jeff Samardzija has relied heavily on his split-fingered fastball and has had a solid season; Lance Lynn was an all-star; and then there’s Chris Sale — the player who made the most seamless transition.
Sale relies on his slider more than all but five qualified American League starters, and while his fastball and changeup combination has been big reasons for his success, the slider without a doubt is his out pitch. As a reliever, Sale got away with being close to a two-pitch pitcher, despite having a solid changeup in college. He used his changeup about 12% of the time against righties, but Sale and the White Sox staff understood the pitch needed to become a more heavily used offering if he was going to be successful in the rotation. Sale now throws the pitch 25% of the time against righties, though he doesn’t use it at all against lefties. The pitch’s success has been a large reason why righties have just a .289 wOBA against Sale — an impressive number for a first-year starter. But even with the success of his changeup, only 21 of the 162 batters he has struck out fell victim to the changeup. The slider, on the other hand, has been the pitch. It’s been used on 95 of his 162 strikeouts and accounts for 59% of his Ks.
The key with the slider is the movement, rather than the speed. At about 79 miles per hour, it’s not a pitch that derives much of its success from power. No left-handed starter in the league averages more horizontal movement with their slider. And his vertical movement ranks No. 4 among all pitchers in the league. His delivery has a lot to do with the movement on the pitch, since the lower your arm slot, the more movement on the pitch. At that arm slot, the roughly 92 mph fastball and the 80 mph slider become more difficult pitches to hit.
As you can see, the pitch is far from overpowering. Still, the pitch’s movement — combined with the deception — made two very impressive hitters look rather silly. One was caught looking, the other whiffed. With Sale’s low arm slot and his low 90s fastball, the slider is deadly against lefties. And since he has such a nice fastball-changeup combination against right-handed hitters, the pitch remains effective.
What’s been especially impressive about the slider is that it wasn’t expected to be Sale’s dominant pitch when he was drafted. For example:
Project Prospect: “There is a chance the slider turns into a quality pitch, but it is currently below-average.”
Keith Law: “He’s thrown a loopy curveball and a harder slider, with a better chance to make the slider work from that low slot, but neither is an average pitch and he primarily works with the fastball and change.”
Sale’s slider development has likely been the biggest key to his career 2.80 ERA in 257.1 innings. The fastball and changeup are key to his repertoire and all three of his pitches are above-average. But it’s his out pitch that allows Sale to be an elite starter, rather than a middle-of-the-rotation arm. His changeup is continually evolving and might soon take over as his primary pitch against right-handed batters, but it’s the slider that’s been most responsible for Sale’s spectacular season.
Thanks to @oakfaninva for the .gifs
Ben has been at RotoGraphs since 2012 and focuses most of his fantasy baseball attention toward dynasty and keeper leagues.