Manchester United captain Nemanja Vidic could be set for an extensive spell on the side-lines after he suffered suspected knee ligament damage.
The Serbia international was taken off after he fell awkwardly under a challenge with FC Basel's Marco Streller as United crashed out of the Champions League.
Vidic went down in obvious distress and immediately signalled to the bench to be replaced.
The Manchester United defender's injury came on a disappointing night for the Premier League champions as they lost 2-1 at St Jacob Park and failed to reach the knockout stages.
Manchester United manager Sir Alex Ferguson now faces an anxious wait to learn the full extent of the problem.
"We don't know with Vidic, we think it's certainly a medial ligament [injury]," said Ferguson. "Hopefully that is the worst of it.
"It looked a bad one at the time," he added. "But he doesn't feel so much pain at the moment.
"Until we get the scan we don't know. I think it maybe medial ligament. Hopefully that's the worst it is."
The Manchester United centre-back was seen leaving the ground on crutches and could be absent for up to four months.