New York Yankees All-Star left-hander Nestor Cortes went on the 15-day injured list Thursday with a strained left groin.

The move was retroactive to Monday. The 27-year-old Cuban is 9-4 with a 2.68 ERA over 23 starts and a career-best 131 innings this season. He is 0-1 over four starts this month.

The AL East leaders also reinstated slugger Giancarlo Stanton from the 10-day injured list after he’d been sidelined by left Achilles tendinitis. He was in the lineup as designated hitter and batting third for the start of a four-game series at Oakland on Thursday night.

Stanton is likely to be the DH for several games initially as he gears up to return to the outfield. Manager Aaron Boone said the Yankees relied on Stanton’s word that he was ready to play again.

“Just kind of listening to him. He knows himself well,” Boone said. “Really excited to get him back.”

Cortes is aiming to help the Yankees for the September stretch run in a rotation that has taken its lumps. New York acquired right-hander Frankie Montas from Oakland at the trade deadline to bolster the starting pitching.

“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 said he felt discomfort in his push-off leg early during his last outing against Toronto on Sunday and pitched through it, wrapping the area for the final three of his six innings. He expects to return on schedule to contribute for the final weeks and playoffs.

He had an MRI to determine the severity of his injury given Cortes was limping after the start. He felt the leg on the second or third pitch of the game but “during the game I didn’t think it was that big of a deal.”

“I might’ve pitched through it. I could’ve gotten worse,” he said.

Cortes played light catch from between 100 and 120 feet at the Oakland Coliseum, making 30-40 throws.

A bullpen could happen in the next few days.

“I’m hoping 15 days is enough,” he said. “I think the fact that I’m feeling pretty well I don’t think there will be any hiccups along the way.”

New York transferred outfielder Harrison Bader to the 60-day injured list with plantar fasciitis in his right foot.

The Yankees signed right-hander Greg Weissert to a major league contract and selected him to the 26-man roster from Triple-A Scranton/Wilkes-Barre.

“He’s going to get some opportunities. He’ll be in the mix, we really like him,” Boone said. “He has kind of rocketed through our system the last couple years, got to Triple-A last year after having a great year, has had a phenomenal year down there this year. Has been on the front of minds really going back to spring training and obviously hasn’t been on the 40 man till now but he’s kind of kicked his way in.”