Any match these days between Manchester United and Celtic is going to conjure up the side issue of their feuding managers but, for Alex Ferguson, there is a third man in the equation this week.

Ferguson may relish the idea of putting one over on Gordon Strachan but Jose Mourinho is the man he really wants to beat and, with that in mind, the United manager is considering taking a calculated gamble at Celtic Park tonight.

Already top of their Champions League group, and needing one point from two remaining matches to qualify, Ferguson has made it clear his priority is Sunday's showdown against Chelsea at Old Trafford. The opportunity is there to go six points clear at the top of the Premiership and Ferguson has spent the past few days mulling over whether it would be sensible, or reckless, to field a below-strength side against the Scottish champions.

Even a manager of Ferguson's reputation is finding it a difficult balancing act, not least because he has chastening memories of gambling with his line-up when the team played FC Copenhagen in Denmark three weeks ago. On that occasion Ferguson left Louis Saha, Gary Neville and Ryan Giggs at home, and put Paul Scholes and Rio Ferdinand on the bench. United lost 1-0 and Ferguson made it clear that he would not gamble in such a way again.

"I am not going to be taking Celtic lightly," he said. "We did all the risking we wanted to in the Copenhagen game. We lost that game and we're well aware of the danger of making too many changes."

He will, however, change a winning team. "We have five days of preparation before the Chelsea game, so there is a temptation to play my strongest team. But I have to give a lot of thought to Sunday as well. There will probably be a couple of changes, though I'm not going to make any more than two."

One of those may be forced on Ferguson, with Neville a significant concern for the United manager. The England full-back has a recurrent problem with a build-up of fluid in both calves and, though he was able to play in Saturday's 2-1 victory at Sheffield United, Ferguson spoke yesterday about the possibility of his captain needing surgery.

"If it happens again we are going to have to take the long-term view and do something about it," said Ferguson. "We need to assess it and find out the reasons why it is happening. He's our captain, a player with great experience, and we want him with us all the time. We don't want to get to the new year and find he's still being troubled."

Strachan may also be forced into one significant switch. Gary Caldwell limped out of Celtic's match against Inverness Caledonian Thistle on Saturday, so Bobo Balde, who has played only twice since April, both matches in the Scottish League Cup, is set to partner Stephen McManus in the centre of the defence.

Like all visiting managers to Celtic Park, Ferguson spent a large part of his press conference yesterday speaking about the need for his players not to be intimidated by the hostile wall of noise inside the stadium.

"Without question it's one of the best atmospheres a player can ever experience," he said. "It's special support. The Celtic players can be inspired by it."

A former Rangers man he expects a lacerating dose of vitriol himself but he seemed comfortable in the knowledge that experienced players such as Scholes and Giggs should not be fazed by the Glaswegian din. United's players have silenced crowds in Italy, Spain and Turkey, and Scholes barely raised an eyebrow when it was put to him that Celtic's supporters might influence the outcome.

"You have to try to block it out," said Scholes. "Everywhere we go the other fans get really behind their team, because everyone wants to beat us. You just get on with it." Scholes recoiled at the suggestion that he was playing the best football of his career to date, as if mystified by the idea, but he has touched some exhilarating heights this season and the debate resurfaced about whether he would reconsider his decision to play for England.

It is a question that Steve McClaren has put to Scholes on more than one occasion since taking over but the answer was an emphatic no. "It wasn't straightforward for me," Scholes explained. "I did give it a lot of thought. It was flattering to have the England manager asking me to return to the team but in the end I decided I didn't want to go back."

The US teenager Freddy Adu begins a two-week trial with United this morning. The 17-year-old has been released for the trip across the Atlantic by his Major League Soccer side DC United.