Williams (ankle) will undergo an MRI on Monday, Ian Rapoport of NFL Network reports.
The MRI should provide more details about the ankle injury Williams sustained late in the Rams' 26-9 victory over the Cardinals on Sunday, when he handled 20 carries for a career-high 158 yards and a touchdown. The second-year pro left Sunday's game without a boot on his injured ankle, but until his MRI results are in, it'll be difficult to project how much time, if any, Williams might have to miss. Meanwhile, backup Ronnie Rivers (knee) is believed to be dealing with a PCL sprain and also will receive an MRI.