Carolina Panthers running back Christian McCaffrey left Thursday's game against the Houston Texans for a sideline medical tent early in the second quarter.
He did not return to the field, and the Panthers ruled him out for the rest of the game with a hamstring injury.
McCaffrey appeared to suffer the injury on a two-yard run early in the second quarter. He pulled up and hopped on his right leg during the run before running out of bounds. A timetable for his recovery was not immediately clear.
The loss is a tough blow for McCaffrey and a Panthers team riding a hot start.