DETROIT -- Already down two members of the secondary to start the game, the Packers lost safety Evan Williams in the first half of Thursday night's 34-31 loss to the Lions because of a concussion.
The rookie walked to the locker room under his own power to be evaluated and did not return.
Zayne Anderson, who had played only eight snaps on defense all season entering Thursday, replaced Williams.
The Packers became even thinner in the secondary as the game progressed. They lost nickel defensive back Javon Bullard in the second half to a right ankle injury that required him to use crutches on his way out of the locker room after the game.
The Packers were without cornerbacks Jaire Alexander (knee) and Corey Ballentine (knee) to start the game. They also were without linebacker Edgerrin Cooper (hamstring).