Is George Kirby's Slider Back? Does Jared Jones Have Fastball Issues?
George Kirby, Jared Jones, Spencer Schwellenbach
Mariners George Kirby is toying with his slider. The pitch averaged 88 mph in his last two starts with <7” sweep. It was 86 mph with 10” sweep in his prior starts. In his last 2 starts, the swing-miss on the pitch doubled from 19% to 38%. His breaking ball success was an issue versus righties this season compared to last. He started throwing a cutter for a pair of outings on 5/13 and 5/19. I thought the cutter was a way to help his breaking balls on the outer third of the plate. Perhaps that was a way to help him start ripping his slider harder? He hasn’t thrown the cutter in either of his last 2 starts. Kirby is a tinkerer and he is tinkering. Based on hitter feedback and velo, the slider looks legit right now. 🔱
Pirates Jared Jones fastball has taken a step back in May. Despite the gaudy stuff score—FanGraphs Stuff+ of 146, #1 in MLB—it’s been SLG-able pitch. Versus lefties, his swing-miss has fallen from 36% in April to 23% in May while his xSLG on the season remains just under .500. Versus righties, we’ve seen him push his location more up-away to stay away from the heart of the zone (see heatmaps below). His four-seam swing-miss to lefties has dipped from 32% to 23% 🏴☠️
It’s a curious case as to why the league has caught up to the four-seam so quickly. While Stuff+ does a great job isolating raw traits that can work, the more we’re able to work with Stuff+, the more you can see limitations. The best orgs develop the stuff and stitch together the mix in the majors (or minors, if you’re the Dodgers). Jones has the raw stuff in spades, and we’ve seen some more changeups in May to lefties which I love, but I’m curious to see his evolution as a pitcher. Add a sinker for righties to give him something inside? Is there room to tweak the slider into a pair of pitches? One with more depth and sweep with another cutter that’s harder (a la Spencer Strider)? I’m fascinated to find out. My bet right now is that the four-seam doesn’t get back to ~35% swing-miss levels without another tweak.
Braves Spencer Schwellenbach had a decent debut: 5 IP, 5 H, 3 ER, BB, 5 K. 5-pitch mix here, ~90% fastball-slider to righties. 96 mph on the fastball is a slight debut boost, he was sitting 95 at Double-A. The shape is more of the cut fastball variety, 12” vertical break, 5” arm-side at a low arm angle with 85th percentile extension. That’s less vertical break and less arm-side than average. It’s below-average shape saved by good velo. Driveline Stuff+ of 117, FanGraphs Stuff+ of 110. I’m surprised the four-seam grades out this well, I expect it to play down off the stuff grades. The intriguing piece of his mix is a hard, depthy slider. 87 mph with -5” vertical break and 5” sweep. That’s ~7” less vertical break than the average slider at that velocity (more drop). 41% swing-miss on this pitch at Double-A. Driveline Stuff+ of 122 on the slider, FanGraphs Stuff+ of 117. 👍
Versus lefties, he breaks out a cutter, curveball, and splitter. 99, 85, and 84 respectively per Driveline Stuff+. He can strike both the fastball and cutter above average, which makes me want more splitter usage, even if it’s out of the zone more. The splitter averaged -2” vertical break at 84 mph, another pitch in his mix with more drop than average. He leans on his curveball a lot because he can land it. It’s a subtle variation off his slider that trades velo for sweep. It’s more sweeper than curveball. I think there’s enough here for him to be a good 4/5th starter. The profile isn’t going to hang gaudy swing-miss numbers, which caps some upside, but his mix doesn’t feel out of place for skipping over Triple-A. I think the slider and curveball are legit. Models like the fastball more than I expected. He’s got a few pitches he can strike to either handedness. Sign me up with some caution due to how I think the four-seam will play.