In what was as much a cruel blow for Newcastle United as for the player himself, Alan Shearer went under the surgeon's knife at precisely 3pm yesterday afternoon ­ kick-off time ­ to have a corrective operation on his injured groin.

It is the third time the England captain has suffered such an injury within the past eight months and raises the worrying question of how long Newcastle will be without the services of their most important player as they pursue success on two fronts.

Shearer first injured his left groin in April last year, but staged an impressive recovery to lead the England attack during the European championship. Covered in glory after becoming the leading scorer in the tournament and then securing a world-record £15 million move to Newcastle, he soon suffered another setback in October.

This time he pulled his right groin and the prognosis was not good. Doctors predicted he would be absent for at least two months, but Shearer, typically, recovered in half the time. The implication now, though, is that he returned too quickly, because he has damaged the same groin once more.

What is certain is that Shearer will be absent for at least a month and that will be damaging enough. He will miss the Uefa Cup quarter-final tie with AS Monaco and the return leg in France two weeks later. The problem for Newcastle is exacerbated by the fact that Faustino Asprilla, his likely replacement, is suspended for the first leg after he was booked for waving a corner flag while celebrating a goal in the previous round of the competition.

Shearer will also be ruled out of several crucial FA Carling Premiership matches, just as Kenny Dalglish, the manager, has placed the club in a challenging position near the top of the table. It is a blow, too, because Dalglish recently sold Paul Kitson, another reserve forward, to West Ham United for a fee of £2.5 million, and even the dependable Les Ferdinand, Shearer's regular striking partner, is carrying an injury.

Given that he has suffered the same injury within the space of three months, Shearer could be sidelined for far longer and that will surely deal a decisive blow to Newcastle's title chances. He will certainly miss top-of-the-table games against Liverpool and Wimbledon and a further month's absence would virtually rule him out for the remainder of the campaign.

Such a scenario is likely, given Dalglish's reluctance to gamble with the fitness of a player he recognises as integral to the long-term future of the club.

When Shearer suffered a serious cruciate ligament injury at Blackburn Rovers, he was restrained from returning ­ even when he protested his fitness ­ for nearly a year by a cautious manager: Dalglish.

The operation yesterday was performed by Gerry Gilmore, a celebrated surgeon who has pioneered a technique to deal with a condition that has become known as "Gilmore's Groin". Shearer spent last night in The London Hospital and Gilmore reported no complications.

"Anyone watching Alan Shearer in recent weeks would agree he hasn't looked himself," Graham Courtney, a club spokesman, said last night. "He has been struggling with the injury and in the end we had no option but to send him in for the operation.

"We are hoping that he will be back to fitness very quickly, but it is difficult to say at this stage. He was unlucky to pick up the same injury, but it does happen occasionally. We are just hoping it will not prove too serious."

Shearer suffered the crippling cruciate ligament injury in December 1992 and it was thought that his career was under threat, but it is the groin problem that has caused consistent worry. He recently explained that his natural build, with such powerful thighs, places an undue strain on his groins.

It is not only Newcastle who will wait through the next few weeks with bated breath and crossed fingers.

Glenn Hoddle, the England coach, is resigned to losing his captain for the international with Mexico at the end of next month, but he must fear a longer absence that would rule Shearer out of the World Cup qualifier against Georgia at Wembley in April.

Dalglish has already been active in the transfer market and yesterday approached Liverpool to ask about the availability of Rob Jones, their England defender. He may now be tempted to look for a forward, however, given his limited cover.