Running back Clinton Portis underwent an MRI on his groin injury on Monday, head coach Mike Shanahan said.
The results were not yet available when Shanahan addressed the media in his Monday afternoon press conference.
Portis suffered the injury early in the fourth quarter of Sunday's game against the Philadelphia Eagles.
"We should find something out in the next couple of hours," Shanahan said.
Later, Shanahan spoke with Comcast SportsNet's Kelli Johnson and said he was "concerned" about Portis's status.
"Anytime he goes out like he did and he puts street clothes on during the game, I'm concerned because I know him," Shanahan said. "I've been around him too long and I know he's going to play hurt.
"Hopefully the MRI is not as bad as I think it might be. We just have to keep our fingers crossed."
Portis, who alternated at running back with Ryan Torain, finished the game with 11 carries for 55 yards. He also caught two passes for 26 yards,
Shanahan praised Portis's performance against the Eagles, saying he "came back with a vengeance" after he was relegated to a third-down role in the Week 3 loss to the St. Louis Rams.
"I thought he was exceptional," Shanahan said. "He played very, very hard, tough football and made some big plays for us."
Meantime, left tackle Trent Williams could be ready for full practice on Wednesday, Shanahan said.
Guard Artis Hicks has sufficiently recovered from the illness that sidelined him mid-game on Sunday.