Roy Keane's latest fitness problem, a damaged knee, was yesterday described as a serious setback for both Ireland and Manchester United. Keane is understood to be preparing for a second exploratory operation in Manchester and a club spokesman said yesterday that a statement on the player would be issued later in the week.

The great fear is that he has torn a cruciate ligament, one of the more serious injuries in football and if this is shown to be true, he could be out until well into the New Year.

It follows a controversial incident in last Saturday's Premiership game against Leeds United at Elland Road when, after becoming embroiled unnecessarily, with Alf Inge Haaland, Keanewas removed from the pitch on a stretcher.

Widely conflicting reports on the extent of the injury were in circulation yesterday but Alex Ferguson denied that it had already been identified as a severed cruciate ligament.

"According to the specialist who examined Roy on Monday, the damage is not long term and as such, there is no substance to reports that he will be out for the remainder of the season," said Ferguson.

"He's had an exploratory operation and a bit of cartilage was removed. His knee is still very swollen, however, and that is a cause for concern. Replacing a player like Keane is very difficult and until such time as we get a clearer idea of how long he's going to be out, its worrying."

Ferguson's sense of apprehension is shared by Mick McCarthy. A time frame of eight weeks, the very minimum being placed on Keane's rehabilitation, would put the midfielder out of both legs of the World Cup play-off if, as expected, Ireland finish second in Group 8.

"At this point I'm in the process of preparing a squad for the game against Romania and I don't want to dwell unduly on what may or may not happen by the time we get round to the play-offs," he said.

"As I understand it, even Alex Ferguson doesn't know what the situation is exactly and it could well be that he will be back playing before the play-offs are over. I simply don't know.

"But having said that, it is, of course, bad news that he will miss at least some games. Its bad news for United and Ireland but most of all, its bad news for Roy himself.

"If necessary, players will be subbed up to replace him in both the Ireland and United teams and we'll just have to get on with it. But the biggest loser is the player himself who will now have to wait and hope that treatment and hard work will get him fit again before long."

From an Irish perspective, the timing of Keane's latest mishap is unfortunate for he is currently enjoying his most successful year in international football and on Tuesday was named in the short list of three from which the Player of the Year will be named later this month.

Even before yesterday's development, McCarthy was reconciled to losing him through suspension for the Romanian fixture. Now, no less than the Manchester United manager, he will await, with some trepidation, the outcome of the second operation.