Manchester United defender Rio Ferdinand trained on Monday, but team-mate Rafael is a doubt for Tuesday's Champions League quarter-final first leg at home to Bayern Munich after missing the session.

Right-back Rafael came off at half-time during United's morale-boosting 4-1 Premier League win against Aston Villa at Old Trafford on Saturday and did not take part in the 15-minute session open to the media at Carrington, the club's training ground, on Monday.

But there was better news for Premier League champions United in the fact that centre-backs Ferdinand (back), Chris Smalling (hamstring) and longstanding absentee Jonny Evans (calf) were all on show at Carrington.

And left-back Alex Buttner, who ended the Villa match with a hamstring complaint, also trained, along with winger Antonio Valencia, who missed last weekend's victory with a knee injury.

United manager David Moyes kept his cards close to his chest when asked about Rafael's chances of featuring against defending champions Bayern in his pre-match press conference later on Monday.

"We have defensive issues, undoubtedly," he told journalists at Old Trafford.

"I won't be giving out my team today, certainly not to Bayern and certainly not to you either. But we will, as everyone is aware, have to make one or two changes."

As expected, star striker Robin van Persie, who earlier this month was ruled out for four to six weeks with a knee problem, did not train on Monday and nor did either the suspended Patrice Evra or England midfielder Tom Cleverley.