NEWCASTLE United are prepared to wait indefinitely for Alan Shearer to re-emerge from his latest injury nightmare.

The Magpies' skipper this week underwent his second operation in little more than four months in a make-or-break bid to cure a tendinitis problem in his left knee.

Shearer is recuperating in Colorado at the clinic of world-renowned knee specialist Richard Steadman, and is expected to be out of action for four months.

But United boss Bobby Robson last night stressed there is no time-limit on Shearer's recovery, raising the possibility that the former England captain could be sidelined for up to six months.

Robson revealed: "He's had a very successful operation. The surgeon is completely satisfied with what he has seen and done.

"He found some problems, but he's hopefully cleared them up and he confirmed the situation is not career-threatening and that Alan will recover.

"He should be back in four months' time, but the specialist will put no time-scale on him playing again. It will take as long as it takes.

"Knowing Alan, he'll try to beat any deadline, so we're not giving him a time to come back.

"His knee is in a brace and he'll be like that for about six weeks. We just have to be patient. He's a good healer, he's got a strong mind, and he'll be back.''

Robson added: "The first operation was a success, and Steadman has said that.

"But Alan got fit, played two matches, felt as though he had a new knee, then jarred it in training.''

United's injury jinx struck again yesterday when full-back Andy Griffin was booked in for a hernia operation - the 14th time a Newcastle player has needed surgery this season.

"Griffin is out for six weeks,'' confirmed Robson. "I've never known anything like it, but neither has our physio, Derek Wright. He says it's the worst season he's had in his life.

"Shearer and Kieron Dyer have both had two operations, and Nikos Dabizas, Carl Cort and Robert Lee have been among the others. And Shay Given broke his nose the other night against Southampton and he's going to have it reset on Tuesday.''

Keeper Given, however, is fit to keep his place for today's visit to Liverpool.

The Republic of Ireland international was expected to miss the Anfield clash with a sprained wrist, a further legacy of a collision with Southampton striker Kevin Davies in Tuesday's dismal 1-1 draw at St. James' Park.

"Shay's wrist has improved dramatically,'' said Robson, who reckons today's opponents are poised to challenge the Premiership rule of Manchester United.

"I can see them challenging Man. United because you don't know what Liverpool have got planned for next season.

"They've always been a club who reinvest money in the team. When they won the European Cup, they always bought again.

"Gerard Houllier has done outstandingly well - it's phenomenal to get to three cup finals in a season - but he's had to make changes slowly.

"He was in joint charge with Roy Evans, a good coach who'd been there a long time, but the club felt that wasn't working.

"Gerard has brought in his own players and he's had the money to do it.

"He's bought people like Didi Hamann, Christian Ziege, Igor Biscan and Nick Barmby, and he paid £11m for Emile Heskey.

"And he hasn't paid bananas for Jari Litmanen. He was supposedly a free, but no player is free when he's coming from a club like Barcelona. Free is just a word agents throw around.

"But he did bring in Gary McAllister on a free and he's been a marvellous acquisition. He always had Michael Owen and Robbie Fowler, and Steven Gerrard has suddenly blossomed - he's an outstanding young player.

"You must never be afraid. We've got nothing to lose, but if we play like we did on Tuesday it might be like the Alamo.

"I went home after the Southampton game and sat up till three in the morning watching a rerun of the match on Sky.

"I can't accuse one player of not trying. The problem was our lack of quality. The players were upset and angry with themselves.''

Winger Stephen Glass, who missed the game with a virus, reported fit yesterday but Robson said: "I'm leaving him out.

"He's appeared, he says he's fit, but he's been ill Tuesday, Wednesday and Thursday. He's had very little food and while he says he's fit, I don't consider him fit enough to play.''

Robson, meanwhile, revealed he has had further one-to-one talks with Marcelino, who United are desperate to off-load.

The £5m Spanish defender, seemingly perpetually injured, refuted claims by fans this season that he is a malingerer.

But despite interest from clubs in Spain, Robson said: "We've had no enquiries for him.

"I've spoken to him this week, now that he's fit. He's training well, as he should - I wouldn't expect anything less than that. We're just waiting to see what will happen.'