Keane has been out for five Manchester United games with a knee injury.

Ipswich skipper Holland said: "It is a squad thing here. The main priority is getting to the World Cup finals and everybody is delighted to see that Roy's available - including me.

"Obviously I'm concerned about my place. I don't like to miss any game and I'm proud of my record, but without a doubt Roy is a big influence for us in Ireland. He's been immense in the last four or five matches and it is a massive boost that he's here.

"He's one of the best in the world. He can do just about everything a midfield player needs to do and he demands the same standards from everybody else. I've certainly been on the wrong end of some of his ear-bashings once or twice."

Ireland manager Mick McCarthy insists Keane has as good a chance as anybody in his 24-man squad of playing in the second leg in Tehran next Thursday as well. But it is thought Keane is ready to give it his all for around 70 minutes on Saturday in the quest to build a big enough lead in the first leg .

Many pundits suggest Keane could need similar surgery to that undergone by Tottenham and Ireland full-back Stephen Carr, who has been ordered to rest until after the New Year by top American surgeon Richard Steadman following a knee operation in September.

On Monday, United chief Sir Alex Ferguson rated Keane "very doubtful" to turn out for Ireland but has clearly left the decision to the player.

McCarthy was delighted when Keane reported to the Irish camp on Thursday, although nearly 48 hours later than most of the Republic squad, and pushed himself through a full training session.

So far, the United star, who was out for 10 months after an operation to repair a ruptured cruciate knee ligament two years ago, has not commented on the speculation he may need further surgery soon.