Logan Webb’s Backwards Sweeper

I’ve been playing around with the new FanGraphs Lab tools a lot recently. At first, it was bug testing, but it pretty quickly turned into fun. One minute, you’re making sure that sliders show up correctly. Next minute, you’re wondering about Logan Webb’s backwards slider. See, Webb throws a big-bending sweeper instead of a gyro slider, but it doesn’t behave at all how you’d expect: It’s good against lefties and bad against righties.
In 2025, Webb put up 5.5 WAR, a career-high mark and his fifth straight season of four or more wins. He used his sweeper a lot to get there. Webb was one of the most frequent right-on-left sweeper users in the majors, and also one of the best. Measured by run value added per 100 pitches, he was 11th in baseball among all righties who threw even 100 such sweepers – and he threw 400 of them. He was 15th in whiff rate for good measure. He was as effective as Paul Skenes was in this situation while going to the pitch three times as often.
But while he was lights out with the pitch against lefties, it fared quite poorly against righties. He was below average, and by a lot. Ninety-one pitchers threw 100 or more right-right sweepers; Webb finished 75th in run value added (or lost, in this case) per 100 pitches. While the league gets about 25% more whiffs with the platoon advantage, his whiff rate with his sweeper was the same against righties and lefties. This all sounds very strange. But when I dug into it, I got some answers. Read the rest of this entry »







