Williams was down for longer than normal, then was examined by athletic trainers and shouted in anger as he headed into the locker room before the workout ended.
Williams' shoulder X-rays showed no break, but he was scheduled to undergo more testing Friday.
Williams might have been upset because he and Scandrick keep getting tangled up. During training camp, Scandrick -- who is battling Mike Jenkins for a starting job -- hit Williams hard enough to knock his helmet off (the chin strap wasn't buckled) and was covering Williams again on a play when Williams landed hard and sprained his wrist.
The Cowboys are counting on Williams to replace Terrell Owens as Tony Romo's top target.
Immediately after the workout, coach Wade Phillips said he had no information about Williams' status, later adding: "I don't know that he's injured. Just wait and see."
"He banged his shoulder a little bit and we're checking on him," Phillips said.
If Scandrick was a little too aggressive for a practice conducted in helmets but no pads, he might have a good excuse: There were 26,460 fans watching. The video boards were in full use and there was even a halftime performance by cheerleaders, giving it a far different feel than any other helmet-and-no-pads workout.
"It's football," linebacker Bradie James said. "I mean, sometimes people run into each other. Hopefully that's all it is."
Fans were let in for free, but paid $10 to park. The concession stands likely did brisk business, too.
Anyone hoping to see punter Mat McBriar hit the video boards went home disappointed. He took about 25 kicks and not a single one reached the world's largest high-definition televisions.
McBriar said no one told him to avoid it. He simply never kicks the ball straight up down the middle of the field and he's not interested in trying just for grins.
"I don't want to get away from what I'm used to doing," he said.
