The Athletics announced this afternoon that they’ve claimed left-hander Joe Rock off waivers from the White Sox. They quickly optioned him to Triple-A Las Vegas. To clear a 40-man roster spot for Rock, the team transferred right-hander Justin Sterner to the 60-day injured list.

The White Sox designated Rock for assignment two days ago after a three-month stint in the organization. He appeared in four games from June 13-24, allowing four earned runs in 10 1/3 innings with 12 strikeouts. Rock also allowed 11 walks in that sample, and he also hit two batters and threw a wild pitch. Largely due to those control issues, the lefty had a 5.65 SIERA and 6.84 expected ERA in his limited action, putting his true talent several runs higher than his 3.48 ERA.

The results haven’t been much better at Triple-A. In 32 2/3 innings for the Rays and White Sox’ top affiliates, Rock has a downright dreadful 6.89 ERA and 18.1% walk rate. To his credit, he has an excellent 28.1% strikeout rate and 50.6% ground ball rate in the minors. Opponents are also batting .407 on balls in play off Rock, which is untenably high. Poor batted ball fortune is only a partial explanation for his struggles, though, as Rock has simply allowed too many baserunners for his strikeout and ground ball tendencies to make a meaningful difference.

For now, there’s little harm in the A’s stashing Rock in Las Vegas as a depth piece. The big league bullpen ranks 19th in the Majors by strikeout rate (21.6%) and 28th by ground ball rate (38.4%). Rock could theoretically help in both of those areas, though he’d obviously need to get the walks under control in order to stick long-term. He posted much more manageable walk rates of 5.7% and 9.3% in 2024 and 2025, respectively, so perhaps there’s room for positive regression as he gets settled at Triple-A.

Sterner’s move to the 60-day IL was expected after he underwent season-ending right knee surgery two days ago. He was a decent bullpen arm last year, as he tossed 65 frames with a 3.18 ERA and an 18.4% K-BB rate. Sterner kept that up through his first 34 innings this year, but he imploded in his last 7 1/3 innings, allowing 13 earned runs in that time. As a result, he’ll finish the season with an ERA over 6.00 and having allowed 2.32 home runs per nine innings. He figures to return when healthy in 2027.

Photo courtesy of Patrick Gorski, Imagn Images