Both players, who were injured in United's FA Cup win at Fulham last Saturday, took part in training on Tuesday. United and Milan drew 0-0 in the first leg.
United manager Alex Ferguson told a news conference on Tuesday he was unconcerned about his poor personal record against his opposite number Jose Mourinho.
Mourinho boasts a remarkable tally of only one defeat in 13 games against Ferguson during his time in charge of FC Porto, Chelsea and Inter Milan.
United are unbeaten in a record 20 Champions League matches and are still in contention for five trophies this season.
"It proves I am not infallible. I am vulnerable to everyone who is involved in football. You can lose football matches," Ferguson said.
"But personal records don't concern me. I look at my football club and I think we have every right to be proud of this football club and what it's achieved over the time I've been here.
"I once had a record at Aberdeen when I couldn't lose at a certain club. I went there with nine reserves once and still won 5-0. Football is a strange game and tomorrow may be even stranger."
Mourinho's most famous result at Old Trafford came five years ago this week when his Porto side scored a dramatic late equaliser to knock United out en route to winning the Champions League.
"I have no nightmares whatsoever (about that). We were the better team beaten by a poor decision and we move on," Ferguson said.
"Many things have happened since then and it's been a very upward trend for us. It was a time of re-building and we now have a fantastic squad which we're very proud of.
"You move on in football, which is what we have done."
Defending champions United, who are undefeated in 18 home matches in the Champions League, were in a similar position in last season's semi-finals after drawing 0-0 at Barcelona before progressing to the final with a 1-0 home win.
"With a 0-0 draw you are never be over-confident simply because an away goal can be a severe setback," Ferguson said.
"That was the situation when we played Barcelona but what was required, as we saw that night, was magnificent concentration and really good focus and we managed to get through on those two factors."
