McCoy left practice on Wednesday with what coach Rex Ryan deemed a "tight hamstring." Ryan did not know the severity of the injury and would not speculate on whether McCoy would be able to play for the Bills (4-2) in their game against the Miami Dolphins (2-4) on Sunday (1 p.m., ET).
McCoy is the second-leading rusher in the NFL with 587 yards, and he has a league-best 5.6-yard average per carry. The 28-year-old is coming off a game in which he rushed for 140 yards and tied his career high with three touchdowns in Buffalo's 45-16 victory over San Francisco.
Tight end Charles Clay (knee) was an active participant after sitting out Wednesday's practice.