Leicester Tigers lock Geoff Parling is unlikely to play again until 2012 after straining medial knee ligaments.
Parling was hurt during last week's Heineken Cup victory over Ulster and had to be replaced after 54 minutes.
But the injury is on the inside of his knee and is not the same one which saw him miss most of the 2010-11 season.
"It's not too bad so we hope it will only be around four to six weeks," director of rugby Richard Cockerill told BBC Radio Leicester.
Parling returned to the Tigers side at the start of October after nine months on the sidelines and has played eight games, including both matches in Europe.
Cockerill added: "Thankfully, it has nothing to do with his old injury. It was Thomas Waldrom getting nudged off the ball and falling over on his legs, so he [Waldrom] is getting a bit of stick at the moment - even more than normal!
"It's just unfortunate and purely bad luck. We seem to be having that a little bit too often at the moment but Geoff will be fine and he will hopefully be fit within the next six weeks."