Detroit Lions coach Jim Caldwell told reporters during his weekly news conference Tuesday that he is "not certain" that defensive tackle Nick Fairley will return this season.
Caldwell also said he has not been told Fairley has been ruled out for the year, either.
"We're not certain how that will work," Caldwell said. "They haven't told me that he wouldn't be at this point in time."
A source told ESPN.com's Michael C. Wright on Monday that Fairley has a sprained knee and that there is hope that he can rehab from the injury in four to five weeks.
"Until we get everything looked at and make a determination, we very rarely put a timetable on it," he said. "I know there was a report out that stated four to five weeks, but it never came from our office because of the fact that we have not come to that conclusion as of yet. When we do, we'll certainly release it."
Fairley injured his knee during the first half of Detroit's come-from-behind 22-21 win over Atlanta on Sunday in London, cutting short what had been his most consistent season to date. After the injury, he had to be helped off the field by trainers and teammates before being placed on a cart and taken to the locker room.
Fairley had 14 tackles and a sack this season in his first eight games. Up until his injury, he had been on pace to play all 16 games in an NFL season for the first time.
Losing Fairley leaves the Lions with three defensive tackles on the roster -- Ndamukong Suh, rookie Caraun Reid and C.J. Mosley, who is currently suspended for a violation of team rules and conduct detrimental to the team.
If need be, the Lions could move Jason Jones or Devin Taylor inside for some defensive tackle snaps or do what they did against the Falcons and play undersized defensive end Darryl Tapp at tackle.
Fairley is in the final season of his rookie contract with the Lions after the team declined to pick up his fifth-year option earlier this year.