NEW YORK — Yankees ace Luis Severino says he hurt his lat muscle warming up before his first scheduled spring training start March 5, though New York's medical staff did not diagnose the injury until April.

When Severino first got hurt, the Yankees said the injury was right shoulder inflammation. After Severino threw on flat ground April 6 and felt like he had not progressed, the Yankees sent him for additional tests and announced the injury to the latissimus dorsi muscle in his back April 9.

General manager Brian Cashman said last week he didn't know "how a lat strain during his rehab process could have occurred." Severino maintains the issue predated the rehab.

"I know something was going on," Severino said Wednesday.

New York's updated timetable from last week estimated Severino could resume throwing around May 21.

Catcher Gary Sánchez hopes to play in Sunday's homestand finale against Kansas City, the first day he is eligible to be activated from the injured list. Sánchez, recovering from a strained left calf, ran Wednesday for the second straight day and intends to resume outdoor batting practice Thursday.

Giancarlo Stanton, who hasn't played since March 31 because of a strained left biceps, started hitting off a machine Tuesday. Manager Aaron Boone said it is too soon to determine whether Stanton can return during the West Coast trip that starts Monday.

New York has 12 players on the injured list.

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