Williams has to be symptom-free for a certain amount of days before being cleared to play. The Cowboys' second preseason game arrives quickly -- Friday, Aug. 9 at Oakland -- and he could miss that game as well.
It's a tough blow for the third-round pick from Baylor because he was the third receiver on the depth chart. With Williams missing the last hour of practice, Cole Beasley replaced him as the slot receiver and Dwayne Harris took over as the No. 3 receiver on the depth chart.