Interim manager Ryan Giggs said a number of United players have been struck down by illness, and are therefore unlikely to play at Old Trafford on Saturday.
Giggs said: "A few of the lads have had a bug.
"Anders Lindegaard has, and so has Wayne.
"Wayne has a tight groin also so obviously with the bug you have to be careful with that because his immune system is down.
"Wayne being Wayne, he wants to be involved so we will just monitor it over the next 24 hours."
Since United beat Norwich 4-0 in Giggs' first game in charge last Saturday, Juan Mata, Rooney and Lindegaard have backed the Welshman to be the club's long-term replacement for David Moyes, who was sacked last week just 10 months into a six-year contract.
United want a more experienced man at the helm though and have held discussions with Holland coach Louis van Gaal.
The former Ajax, Barcelona and Bayern Munich coach could be appointed early next week. Giggs is yet to decide whether he would like to be part of Van Gaal's staff.
"Nothing has changed. (This job) is just until the end of the season," Giggs said.
"We will chat when the season is over.
"The main concentration I have is on the Sunderland game and then after that the remaining two games.
"I have a lot to think about - whether to continue playing...
"But my concentration is just on now. We will see what happens at the end of the season."
Giggs has been handed a boost ahead of the Sunderland game with the news that Robin van Persie is back in training.
The Dutch striker has been out with a knee injury since scoring a match-winning hat-trick in United's victory over Olympiacos on March 19.
"Robin has looked good in training this week," Giggs said.
"We will see (after training) today whether he is ready for tomorrow."
Giggs is sure to receive another rapturous reception when he emerges from the tunnel - just as he did last Saturday when he confidently strode down the touch line in his official club suit.
Giggs is reluctant to swap the suit for his United kit, which opens up the possibility that the 40-year-old, who is out of contract in the summer, may never again play for the team he has supported all his life.
"I have kept myself fit, but I might not get back in (the team)," said Giggs, who has made a record 962 appearances for the club.
"The lads have been doing well. We will just have to wait and see."
Following the win over Norwich, Giggs spoke of the agony he felt at dropping some of his team-mates like Mata for the match.
The midfielder has been getting to grips with other aspects of the job this week, mainly in the planning department.
Giggs may not be at the helm next term, but executive vice-chairman Ed Woodward has been seeking the interim manager's thoughts on next season at the AON Training Complex.
"The only peace and quiet you do get is when you are on the training pitch," Giggs added.
"As soon as you are back in the office, you have meetings, and you have calls...
"For example this week has been planning pre-season, which has been testing because we have to wait and see about the Europa League and the Q3 for that is round about the tour time, so there are different permutations.
"Also it is a difficult time for young players, extending contracts, renewing contracts, loan players, players that need to come back, players that need their future sorting out so there has been a lot of that this week."
Giggs will also find himself in another unusual situation this weekend when he tries to manage a team to victory over former team-mates.
"It will be great to see Wes (Brown) and John O'Shea back," Giggs said of the former United duo, who left for Sunderland in 2011.
"They are in really good form, and Phil Bardsley is as well.
"The service they have given to this club will never be forgotten. They were great team-mates."
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