The Swedish international has been struggling with the problem all season and was forced to miss training last week.

Mellberg is set to be rested for Wednesday night's Worthington Cup clash with Oxford, but he admitted if rest does not cure the problem he may have to go under the knife.

"This can't go on forever. If it doesn't help, then we might have to look at some other treatment," said Mellberg.

"I didn't train at all last week as I was just looking to be fit for Blackburn.

"I feel the same way as then but perhaps even a little bit worse. It would have been very difficult to play tonight and this coming Saturday.

"I'm in every day, doing strength work and stretching, trying to build it up and to see if that helps. I hope that we're looking at the Fulham game."