The Eagles said Asomugha would undergo further evaluation - likely an MRI exam - before they make a final diagnosis. Several players were optimistic that he would return sooner rather than later.
"It looked bad, but they said he was going to be all right, expecting to come back tomorrow and practice," cornerback Joselio Hanson said.
When Asomugha left practice - he was listed as a partial participant - reserve Brandon Hughes took his spot at right cornerback opposite Asante Samuel. Under normal circumstances, Dominique Rodgers-Cromartie would be the first substitute, but he has a high-ankle sprain and is out for Sunday.
Hanson has filled in for Rodgers-Cromartie as the nickel corner, but he said that if Asomugha couldn't play against the Patriots he would move outside in the base defense and then into the slot when a fifth defensive back was needed.
In that scenario, Hughes - who has been the dime corner the last two weeks - would slide outside and rookie Curtis Marsh would take his place as the sixth defensive back.
"I've just been waiting for an opportunity," Hughes said. "That's kind of the nature of the business, if he is injured then another guy has to step up - whether it's me or somebody else. . . . I feel good about the game plan. I feel good about what I can do."
The Eagles signed the 5-foot-11, 188-pound Hughes off the Giants' practice squad last November. He was drafted by the Chargers in the fifth round in 2009. He has played primarily on special teams this season.
Losing Asomugha would be a blow to Juan Castillo's defense. The Eagles' high-priced free-agent acquisition hasn't quite played up to his five-year, $60 million contract, but his struggles can be partly attributed to his ever-changing role.
He has played in various spots and was likely going to be asked to do the same against the Patriots, who present a number of matchup problems. Asomugha was bound to cover prolific tight ends Rob Gronkowski and Aaron Hernandez at some point Sunday.
"There are different packages that we have," Castillo said when he was asked, prior to Asomugha's injury, about his game plan for covering the tight ends. "And I think that they know sometimes Nnamdi will be there, sometimes he won't be there. It could be two guys or one guy or maybe a safety."
If the Eagles keep Hanson strictly in the slot, Hughes said he was confident he could handle all of Asomugha's responsibilities.
"They use Nnamdi in so many different ways," Hughes said. "I'm quite sure if they ask me to do it I can do it."
Marsh, selected in the third round of April's draft, was active for the first time last week against the Giants and played on special teams. Light at corner a year ago, the Eagles made significant additions with Asomugha and Rodgers-Cromartie in the offseason, and with Hughes and Marsh the team considered the position one of its deepest.
"Brandon - he's really good, and he's coming into his own with more game experience," Coleman said. "With Curtis, he's athletic. He loves to be able to get up there and bump and run, and he has the speed to run with any wide receiver."
Asomugha has never missed more than two games in any of his previous eight NFL seasons. The most significant injury of his career was a broken ankle he suffered as a freshman at California.
The general mood emanating from the Eagles locker room was that Asomugha's knee injury wasn't serious.
Contact staff writer Jeff McLane
at 215-854-4745, firstname.lastname@example.org, or @Jeff_McLane on Twitter.