Injured powerhouse Marcus Bai remains positive despite being told he could miss three months of action.

The 34-year-old Bulls winger, who plans to retire at the end of the season, damaged medial ligaments in his right knee at Harlequins on Saturday.

A scan has confirmed he will be out for up to 12 weeks but upbeat Bai insisted: "I'm hoping to be back in eight, maybe less.

"It's really frustrating and it will be weird sat on the sidelines I haven't had an injury for six years but I'll stay positive, work hard in rehab and see what happens."

It is a blow for the champions both in the short term they have a huge Powergen Challenge Cup clash against St Helens on Saturday and long term as the side continue their Super League defence.

Bai has been a revelation since signing from Leeds last winter, despite his capture originally being met by some fierce criticism.

He was only brought in on a 12-month deal to help replace the far younger departing duo of Bradford-born Great Britain internationals Stuart Reardon and Leon Pryce.

Some supporters questioned the wisdom of such an acquisition but the Papua New Guinean international has left those knockers eating their words.

He has been one of the Bulls' most consistent and potent performers, playing every match and scoring ten tries including six in the last seven fixtures.

But it is not just his finishing prowess that will be missed. Bai's work-rate is second-to-none, he is a fierce ball-carrier who plays like an extra forward and his surges have proved a major asset.

Bulls boss Steve McNamara said: "It's a big blow. Marcus is a good bloke to have on and off the pitch.

"He does a lot of the hard stuff, the early carries and the tough carries in the set.

"Marcus gets us going forward there and that's on top of all his tries. He's been fantastic for us this year but now his injury gives someone else an opportunity to really step up and make a mark."

Karl Pryce is the obvious candidate but the 19-year-old out of contract at the end of the season could do with some form of his own after some indifferent appearances so far.

Andy Smith has been scoring tries for fun in the Senior Academy, while full back Marcus St Hilaire can also fill in on the wing and offers experience.

Bai, who won Grand Finals with Melbourne Storm in Australia and then Leeds, must wear a leg brace for five weeks, just as team-mate Brad Meyers did earlier this season. He was crocked for two months.