ESPN Bills reporter Mike Rodak discusses LeSean McCoy's early exit from practice and when he could return to the team. (1:16)

ORCHARD PARK, N.Y. -- The Buffalo Bills pulled star running back LeSean McCoy out of practice Thursday after he experienced tightness in his hamstring.

"Do I expect him to play?" coach Rex Ryan said. "I certainly hope so."

The Bills host the New England Patriots on Sunday. If McCoy isn't able to play, the Bills would turn to rookie Karlos Williams, the team's leading rusher in their Week 1 win over the Indianapolis Colts.

"I don't even want to think that way, but yeah, it would be definitely [next man up]," Ryan said. "But like I said, I'm not giving up on McCoy playing."

McCoy suffered a hamstring injury during training camp. He was removed from the injury report Wednesday.