Sir Alex Ferguson's increasingly precarious relationship with Nemanja Vidic has deteriorated even further after the unsettled defender pulled out of Manchester United's Champions League match against Milan.

United will have to face the seven-times European Cup winners without their reigning player of the year and, despite his natural reluctance to question his players in public, Ferguson could barely disguise his irritation as he explained why the Serb had withdrawn from the travelling party.

Vidic has missed the last nine matches since withdrawing from the FA Cup third round tie against Leeds United on 3 ­January, citing a nerve problem in his calf, but Ferguson had been certain that a defender who has been renowned in the past for his desire to put himself on the line for his team would be in ­contention tomorrow. Vidic's withdrawal is ­understood to have gone against the feelings of the club's medical staff and Ferguson hinted at major doubts about the player's commitment.

"It's a difficult one because he feels he needs to do a lot of training," Ferguson said. "He has been training for the last 10 days but he still does not feel he is ready to take part in games. That's something we just have to be patient with and that's what we are doing at the moment."

The manager's tone was one of exasperation rather than sympathy, ­leading to questions about whether he saw Vidic remaining at the club beyond the end of next season. Ferguson robustly insisted there were no plans to sell him but his frustration was evident going into a tie in which he already has misgivings about Rio Ferdinand's involvement in the centre of defence.

Ferdinand has been involved in only two matches during four months in which he has had intensive treatment on his recurrent back problems, and ­Ferguson admitted that he would have to think closely about whether the England international should be involved or whether it was too risky.

"There's nothing wrong with him mentally but anyone who has had a back injury, even if they are not a sportsman, will know how difficult it can be," he said. "We have put a lot of work into him and he has trained very well. He hasn't missed a session in the last six or seven weeks. We have to make a decision whether he is right to play."

Ferguson went on to say that he planned to use Ferdinand from the start but it is anything but ideal preparation before a match in which Ryan Giggs will be another notable absentee. Privately, Ferguson is said to have informed colleagues that Vidic does not "want to hang around" and this is not the first time he has expressed ­frustration with the Serb's newly acquired habit of pulling out of matches at late notice. When he withdrew from the Leeds tie during the warm-up an exasperated Ferguson admitted that he "couldn't tell you" why. The 28-year-old did the same before the game against Arsenal on 31 January and, in the meantime, has repeatedly been linked to, among others, Milan.

Ferguson conceded that "a lot of clubs want to buy our players." Asked if he wanted to keep Vidic, he replied: "Of course we want him to stay. He's a great player, one of the best centre-backs in the world. Of course we want to keep him."

The game will see David Beckham face United for the first time since leaving the club in 2003, and the former England ­captain made it clear he harbours no bad feelings towards Ferguson despite the acrimonious manner of his departure.

Beckham described his former ­manager as a "father figure" and insisted he had only good memories of his time at the club. "He always has been and he always will be. No matter what has been said in the past, whether good or bad, I only remember the good times," he said.

"He was the man who gave me my chance to play for club I had always dreamed of playing for.

"For me they were only good times. Sir Alex is respected throughout ­football all around the world. Clubs move forwards and it was my time to leave Manchester United in 2003, and I moved on. I definitely hold nothing against the manager, he's an incredible man."