Roy Keane's attempt to prove that he has distanced himself from the knee problems which have fragmented his season to date is set to reach a critical point at Marseille tonight (live Network 2, kick-off 7.45). After making a belated appearance in Manchester United's Premiership win over Watford on Saturday, Keane is now in line to start their return Champions League game against the French club.

And that will please Mick McCarthy as he looks ahead to the first instalment of the European Championship play-off against Turkey at Lansdowne Road on November 13th.

The announcement of McCarthy's preliminary squad for that game is still a fortnight away but the certainty is that it will be coloured in part by the progress of the Manchester United midfielder if, as anticipated, Alex Ferguson names him in his starting line-up.

After resting his suspect knee for a fortnight, the club captain was back in light training last week and did enough to convince Ferguson that he was capable of playing in at least part of the Watford game.

Replacing Jaap Stam in central defence at a stage of the game when Watford's brittle challenge was already broken was never going to be the litmus test of Keane's fitness. This evening's game certainly is, however, as the European champions seek to bring their title defence back on track.

If he survives what threatens to be a tense struggle for midfield control, he will be seen to have made a telling statement about his capacity to make a substantial contribution to the remainder of United's and Ireland's seasons.

If he doesn't and the club's medical advisors see fit to recommend an operation to strengthen his knee, his career could again be on hold for the remainder of the season.

That's a scenario that neither Ferguson nor McCarthy wishes to contemplate at this stage. Speaking after the Watford game, Ferguson said that he was reassured by what he had seen.

"It was never going to be too taxing for him playing at centre back but I thought he did what he had to do with his usual efficiency," he said. "He, himself, was pleased with his performance and if he now feels that his knee is okay, there is no reason why he shouldn't start against Marseille.

United will equal an all-time European record held by Ajax if they avoid defeat in the Stade Velodrome. Since losing to Juventus in December 1997, they have gone 18 games without defeat and will equal the record set between 1994 and 1996 if they win or draw. More importantly a victory will see United almost certainly through to the next phase of the competition.

Ferguson added: "We go to Marseille top of the group and when we play away from home in Europe we have a good record and are always a threat on the break. That is how we will approach this game - they know we are a big danger on the break. We can always score away and that is such an advantage to in Europe."

Ferguson has to chose between Raimond Van Der Gouw or Mark Bosnich in goal but has Ryan Giggs fit again and Gary Neville could be risked after missing the past month with a knee problem. He may be asked to fill a central defender role as Henning Berg is still doubtful with a knee injury.