Williams (quadriceps) isn't practicing Wednesday, Darren Urban of the Cardinals' official site reports.
Williams injured his quad in the second half of Sunday's 20-15 loss to the Redskins, leaving Elijhaa Penny and D.J. Foster to split backfield work in the fourth quarter. Penny likely would serve as the lead runner if Williams were to miss Sunday's game against the Giants, with Foster potentially also taking on a larger role than usual. Bronson Hill, who was re-signed Tuesday, might also factor into the backfield equation.