1 of 5 | Veteran slugger Giancarlo Stanton last played for the New York Yankees on April 24. File Photo by John Angelillo/UPI | License Photo

Aug. 22 (UPI) -- New York Yankees slugger Giancarlo Stanton sustained a left calf strain, putting his potential return in jeopardy, manager Aaron Boone told reporters Saturday.

Stanton sustained the injury while rehabbing a right calf strain. The five-time All-Star hasn't played for the Yankees in four months.

"He unfortunately strained his other calf in his running a couple days ago, had fallen and the other calf is strained," Boone said. "It's a moderate grade. So, what that means moving forward, we are not ruling anything out. He'll obviously continue to work to get it right and hopefully be available.

"But obviously, we are at a point in the calendar where it gets challenging. You also never know."