Image credit: (Photo by Bill Mitchell)
At its best, the Arizona Fall League features the stars of tomorrow. This year’s World Series featured AFL alums Corey Seager, Marcus Semien, Merrill Kelly and Gabriel Moreno, among others. The league also serves as a six-week exhibition for players who might not always grab the headlines. That’s especially true for players on the bubble for 40-man roster protection.
Here—with the use of Statcast data, video and BA’s Stuff+ model—we’ll highlight five pitchers whose stuff—be it one pitch or an entire arsenal—jumped off the page during their time in the Fall League. One of those pitchers, Jackson Jobe, is a Top 100 prospect and a household name in prospect circles.
The other four don’t fit that bill. The group is fairly anonymous, but they have pitches that stand out now and might help them get to the big leagues in a few years.
Jackson Jobe, RHP, Tigers
Four-Seam Fastball (119 Stuff+), Slider (134 Stuff+), Cutter (134 Stuff+)
Jobe is far from under the radar. With three pitches that score so highly on BA’s Stuff+ models, it’s easy to understand why he’s held in such high regard. After recovering from injuries, Jobe was dominant. He moved from Low-A to Double-A during the regular season. At High-A, he struck out 54 hitters and walked just three in 40 innings. He added 19 strikeouts in 15.2 frames in the AFL.
Justin Slaten, RHP, Rangers
Slider (127 Stuff+)
Slaten was the Rangers’ third-rounder in 2019, out of New Mexico. He shifted to the bullpen in 2022 but hadn’t put up particularly good numbers until this past season, which he spent mostly at Double-A before a few innings at Triple-A to finish the year. He struck out 86 in 59.2 innings, helped by a slider with respective miss and chase rates of 44% and 35%.
Jarod Bayless, RHP, Mariners
Slider (133 Stuff+)
Bayless was selected by Seattle out of Dallas Baptist, where he was a reliever for two seasons. He got hit around at High-A Everett in 2022, then began 2023 back a level, at Low-A Modesto. He made it back to High-A on May 7, then proceeded to dominate the Northwest League. He threw 41.2 innings over 33 games, when he struck out 50 hitters and walked just four. Bayless’ sweeping slider was thrown for strikes at a rate of nearly 71% and got misses and chases at rates of roughly 32% and 34%.
Juan Mejia, RHP, Rockies
Slider (133 Stuff+)
Mejia signed with the Rockies in 2017 out of the Dominican Republic. He’s moved slowly through the system since then, and has been a relief-only prospect since 2018. He’s never put up knockout numbers, outside of the strikeout category. He’s struck out roughly 11 hitters per nine innings over the course of his career, a figure that peaked in 2023, when his rate moved to 13.2 K/9 between High-A and Double-A. The pitch sits around 85 mph with spin rates around 2,650 rpm and got whiffs at a rate of 48%.
Jacob Wallace, RHP, Royals
Slider (122 Stuff+), Four-Seam Fastball (108 Stuff+)
Wallace was originally drafted by the Rockies out of Connecticut in the third round in 2019. Since then, he’s flashed big-time stuff but struggled with control and command. Even so, the Red Sox and Royals have each thought enough of his upside to acquire him in trades. Boston got Wallace in exchange for Kevin Pillar and Kansas City received him in a deal that sent Wyatt Mills to the Red Sox. The 25-year-old struck out 57 hitters in 49.1 innings at Double-A Northwest Arkansas, but he also walked 40 hitters and allowed 46 hits. Wallace’s stuff will get him plenty of chances, but he’ll need to harness it a whole lot better.