The New York Yankees activated outfielder Giancarlo Stanton from the 10-day injured list on Thursday and placed left-handed pitcher Nestor Cortes on the 15-day IL because of a groin injury, it was announced.

Stanton hasn't played since July 23 because of left Achilles tendinitis. He went through live batting practice on Tuesday and his activation ahead of the game against the Oakland Athletics was expected. Stanton was slated to bat third in Thursday's game as the designated hitter.

To replace Cortes on the active roster, the Yankees promoted minor league right-hander Greg Weissert. Outfielder Harrison Bader was also transferred to the 60-day injured list.

Cortes said he felt discomfort on Sunday during his start against the Toronto Blue Jays.

"I feel like if there was a time for it to happen it would be now instead of the middle of September or late September going into the playoffs or October," Cortes said. "I've got to take care of my body so I can be one of the guys when playoff time comes around."

Cortes has been one of the best pitchers in baseball this season, posting a 2.68 ERA over 131 innings and making his first All-Star Game earlier this season. He has blown past his previous career high in innings pitched and never topped more than 115 in the minor leagues. Cortes sits second in the Yankee rotation in fWAR with 2.6, behind Gerrit Cole.

The Yankees enjoyed a clean slate of health throughout the first half of the season but have been dealing with many injuries of late. Yankees manager Aaron Boone is now down to Cole, Domingo German, Frankie Montas and Jameson Taillon in his rotation.

One possible solution would be to move Clarke Schmidt into the rotation. Schmidt has mostly been in the bullpen for the Yankees this season but was stretched out to pitch starter innings when he was briefly sent down to the minor leagues.

The Yankees are also expecting Luis Severino (lat strain) to return to the rotation from the injured list by mid-September. In the bullpen, Zack Britton made his first minor league appearance Wednesday since undergoing Tommy John surgery in September and closer Clay Holmes (back) could rejoin the team from the IL in the near future.

Weissert has pitched in 40 games for the Scranton/Wilkes-Barre RailRiders this season, posting a 1.76 ERA with 18 saves and 67 strikeouts in 46 innings.

The Associated Press contributed to this report.