Athletics Claim Joe Rock Off Waivers From White Sox

The Athletics added some pitching depth Sunday, claiming left-hander Joe Rock off waivers from the Chicago White Sox and immediately optioning him to Triple-A Las Vegas.

To make room for Rock on the 40-man roster, the Athletics transferred right-hander Justin Sterner to the 60-day injured list.

Rock, 26, has had a busy 2026 season. The White Sox acquired him from the Tampa Bay Rays in May in exchange for infielder Oliver Dunn, but his time in Chicago lasted only three months. The White Sox designated him for assignment two days before Oakland claimed him.

Rock made four appearances for Chicago between June 13 and June 24, working 10 1/3 innings. He allowed four earned runs and struck out 12 batters, but his command was a major concern. Rock also issued 11 walks, hit two batters, and threw a wild pitch during his brief stint in the majors.

Control has been an ongoing problem for Rock throughout the season. Although he posted a 3.48 ERA in the majors, his 5.65 SIERA and 6.84 expected ERA suggest his results were better than his underlying performance.

His numbers at Triple-A have been even more concerning. Rock owns a 6.89 ERA across 32 2/3 innings while walking 18.1% of the 171 batters he has faced. He also hit six batters, meaning more than one-fifth of opposing hitters reached base against him via either a walk or hit-by-pitch.

There are still some positives in Rock’s profile. He has posted a 28.1% strikeout rate and a 50.6% ground-ball rate in Triple-A this season. Opposing hitters have also carried an unusually high .407 batting average on balls in play against him.

Before 2026, Rock had been considerably more effective in the minors. From 2023 through 2025, he recorded a 4.79 ERA, 23.1% strikeout rate, and 7.5% walk rate across 329 minor league innings.

Rock transitioned primarily into a relief role this season, which could give the Athletics another potential bullpen option down the road. He remains optionable for the rest of 2026 and has another option year available, giving Oakland some flexibility with his development.

For now, Rock will provide additional depth in Las Vegas. The Athletics could eventually look to his strikeout and ground-ball ability to bolster a major league bullpen that ranks 19th in MLB with a 21.6% strikeout rate and 28th with a 38.4% ground-ball rate.

The biggest question will be whether Rock can regain control of the strike zone. If he can reduce the walks and hit-by-pitches, his swing-and-miss ability and ground-ball tendencies could make him an intriguing bullpen option for the Athletics.

Meanwhile, Sterner’s move to the 60-day injured list comes after he underwent season-ending surgery on his right knee. He ends the 2026 campaign with an ERA above 6.00 and 2.32 home runs allowed per nine innings after surrendering 13 earned runs across his final 7 1/3 innings.