Sir Alex Ferguson has confirmed Nani is set to face Marseille on Tuesday after he returned to training on Monday.
Nani suffered a gash in his leg in a high challenge from Jamie Carragher during the 3-1 defeat at Liverpool, and Ferguson had said on Friday that he would not be available for United until after the international break.
However, the Manchester United manager revealed this weekend that Nani had recovered more quickly than expected and could be available for Tuesday's Champions League tie at Old Trafford.
Nani then made a return to training on Monday morning and, afterwards, Ferguson said at a press conference: "There's a good chance he'll be involved. He and Michael Carrick trained on Sunday. Both will be involved tomorrow [against Marseille]."
"It's great to have [Valencia] back," Ferguson said. "The question is should I play him from the start. It's a fantastic bonus to have him back."
Park Ji-Sung, recovering from a hamstring injury, was taking part in separate fitness work with one of the coaches, while Owen Hargreaves - who sustained a hamstring injury six minutes into his most recent comeback in November - was training with the reserves.
"The key is to have everyone available," Ferguson said. "We're in three competitions. Ji-Sung Park is making good progress - we'll hopefully have him back for Saturday [against Bolton].
"Owen Hargreaves started training. You never know, we may have him available for the end of the season. The important thing is to have players for the run-in. If you do that then it increases our chances [of success]."
"He got a knock in Saturday's game," Ferguson said. "He was getting treatment on it this morning and so couldn't train."
Vidic is expected to be available to face Marseille, though, but Darren Fletcher appears more doubtful after he missed out on the training session due to a virus.
Ferguson was keen to emphasise Marseille's quality as United look to improve on their performance in the 0-0 draw at the Stade Velodrome.
"We have to recognise Marseille are an experienced, powerful side," he said. "They've showed their qualities away from home and that's what we'll be up against on Tuesday."