CLEVELAND — Concerns about the Yankees’ starting rotation deepened on Sunday when Domingo German, who entered the day tied for the major league lead with nine wins, landed on the injured list with a strained left hip flexor muscle.
German, who kept the discomfort quiet until Saturday, is slated to have a magnetic resonance imaging examination in New York on Monday.
“I thought I would overcome it,” he said before the Yankees defeated the Cleveland Indians, 7-6, in 10 innings on Aaron Hicks’s run-scoring double. “I tried not to move a lot so that I could overcome it. When I sat for a while in the dugout and stood up again, I couldn’t because getting cold the pain was worse.”
German, 26, had been a godsend to the Yankees’ rotation, which has endured several injuries, notably to the ace Luis Severino, who may not return until after the All-Star break. But German’s earned run average shot up to 3.86 from 2.60 over his past three starts.
That coincided with when he began feeling discomfort in his hip. He said it hurt only during games until Friday, when he coughed up four runs over six innings in a 5-2 loss to the Indians. It bothered him most in the second inning, but he continued on.
“I lost power when the innings went on and the pitch count rising,” he said.
German, a right-hander, told the Yankees of the pain on Saturday when he struggled to land on his left leg during his regular throwing between starts.
Yankees Manager Aaron Boone said that the team had encouraged players to speak up about any physical issues, but he noted that there wee inevitably little discomforts throughout the long season that did not rise to the level of an I.L. stint.
It was not clear how much time German will miss, but the Yankees hoped it would be a brief absence.
Because they have a day off on Wednesday, the Yankees do not need a fifth starting pitcher until June 17. They have used an opener when they were short on starting pitching, such as Sunday, when Masahiro Tanaka was o supposed to start. He was pushed back to Monday against the Mets because of the birth of his daughter.
Regardless, the Yankees are likely to explore starting pitching additions ahead of the July 31 trading deadline. Last week, the Yankees were outbid for the free-agent starting pitcher Dallas Keuchel, who signed with the Atlanta Braves for $13 million for this season.
C. C. Sabathia has served two I.L. stints for his balky right knee. James Paxton, who is slated to start on Tuesday, missed some time with a left knee injury. Before his ailment, German faced an innings restriction because of his past workload. Severino has not thrown a pitch this season.
Still, the Yankees’ rotation entered Sunday with a 3.92 E.R.A., eighth best in the major leagues. But the stout bullpen has carried a heavy load. Several relief pitchers are on pace for career highs in appearances, and Dellin Betances had a setback last week during his rehabilitation from a shoulder injury.