The NFL suspended Patriots rookie RB Brandon Bolden four games for violating the league’s policy on performance-enhancing substances.

Bolden, an undrafted rookie out of Mississippi, has not played since Week Six because of a knee injury. In his six games, he has 43 carries for 234 yards and two touchdowns, as well as two catches for 11 yards.

Against the Bills in Week Four, Bolden carried the ball 16 times for 137 yards. Shane Vereen and Danny Woodhead will be the Patriots’ backs behind Stevan Ridley during Bolden’s suspension.