Stuart Fielden has been forced to undergo an operation on the knee injury which he sustained during Sunday's victory at London.

In another blow to the Great Britain front rower, Fielden yesterday underwent minor surgery on his right knee, following a crunching challenge with London's Nigel Roy.

Fielden missed nine matches with a ligament injury to his left knee sustained in April, before injuring his ankle two matches into his comeback.

He will miss the crunch clash with Leeds on Sunday but coach Brian Noble is hoping for a rapid return, as the regular season enters its

climax before the play-offs begin.

But the Bulls boss admitted: "I've no idea at all this stage how long Stuart will be out for and we will have to just wait and see."

Noble could however be boosted by the return to fitness of winger Lesley Vainikolo and utility back Leon Pryce for Sunday's Odsal clash, where a victory would see the Bulls become Minor Premier champions.

Both missed the London match and Noble said: "Lesley and Leon didn't participate in full training yesterday and we won't know about their availability until Thursday or Friday." Despite the absence of the hugely influential Vainikolo and Pryce, Karl Pratt returned to the side at London and was hugely instrumental in the 56-12 drubbing.

And if Pryce is passed fit, Noble will be forced to endure a major selection headache for the Leeds clash.