Mackensie Alexander exits with hamstring injury in Tigers' loss

Mackensie Alexander injured after making tackle (0:50)

Mackensie Alexander goes in to make the tackle against Alabama, but he injures his hamstring and leaves the game. (0:50)

GLENDALE, Ariz. -- Clemson All-America cornerback Mackensie Alexander injured his left hamstring in the College Football Playoff National Championship Presented by AT&T and didn't return in the Tigers' 45-40 loss to Alabama.

Alexander was a game-time decision Monday because of an injury to his right hamstring suffered in the CFP semifinal against Oklahoma. He started against Alabama and made two early tackles before he had to be helped off the field in the second quarter. He required help to enter the locker room before halftime.

Alexander, a redshirt sophomore, was a critical player for the Clemson defense, a shut-down corner who was expected to match up with Alabama receiver Calvin Ridley, the Tide's best deep threat.