Martin Prado, one of the few Yankees to show any consistency with the bat of late, sat out Wednesday night's game and could be out for more games than that.
The utilityman, hitting .381 with four homers and 11 RBIs over his last 16 games, suffered what Joe Girardi called "a mild, mild strain" in his left hamstring while running the bases in Tuesday night's 9-4 loss to the Red Sox.
"I don't know if he'll be in there tomorrow, but right now he's down," Girardi said.
Prado spent the day getting treatment.
"I think we made a little progress today," he said after Wednesday night's 5-1 victory.
"We'll see how I respond tomorrow, but we did everything we could today to make some progress."
The injury occurred during Prado's third at-bat when he reached base on an error by Red Sox third baseman Will Middlebrooks, taking a big turn at first.
"I thought I could make it a double," Prado said. "I stopped between first and second and felt something I never felt before and I told them."