Boston Red Sox outfielder Mookie Betts left after the fourth inning of Saturday's 12-6 loss to the Tampa Bay Rays with right hamstring tightness.
The star outfielder exited after hitting a double in the fourth.
"He tweaked his hamstring running around the bases," Boston manager Alex Cora said. "It was just tight. He's day-to-day, so we'll see how he is."
Blake Swihart entered the game to take Betts' place in left field, with Andrew Benintendi and Jackie Bradley Jr. shifting to center and right field, respectively.
Betts is off to a sizzling start for the Red Sox this season with a .344 batting average, eight home runs and 18 RBIs.