The 23-year-old still hasn't recovered from the hamstring injury he picked up against Wigan a month ago and has missed United's six games since.
Many expected the England international to return for the Premier League clash with West Ham last weekend but the forward failed to make the bench.
Now it has been confirmed that the club do not want to rush the former Everton star back.
ImportantUnited have some crunch games on the horizon, including the first leg of the last-16 tie with Inter Milan in the UEFA Champions League on February 24th.
"We are still assessing Wayne," assistant manager Mike Phelan said.
"He has done a little bit of work but we are not going to rush that situation because we have important games.
"We will ease him back in as quickly as we can.
"If he is available terrific, if not we will look at the next game against Fulham because we would never jeopardise anything."