United were denied by a late equaliser as they drew 1-1 with Anderlecht in Brussels, with Henrikh Mkhitaryan scoring a vital away goal midway through the first-half.
Rooney missed that match with an ankle injury and hasn’t played for United since their 0-0 Premier League draw with West Brom, at the start of the month.
However in his pre-match press conference Mourinho told reporters that Rooney had a chance of making the substitutes’ bench for the second-leg of their Europa League tie.
“He's working now, he's improving and if in this training session [this afternoon] the answer is positive, I would select him to be on the bench tomorrow,” Mourinho commented.
“He's experienced and has know-how of this knockout phase – I think he's a player that can be useful tomorrow.
“If we need a goal, he can help us. If we need to keep a result, to keep the ball, to keep control of the game by having possession, he can help us too. So, hopefully his answer in the training session is positive.”
While Rooney is set to make a return, Mourinho confirmed that United’s other absentees remain side-lined.
Juan Mata is likely to miss the rest of the season with a groin injury, while Chris Smalling and Phil Jones are also unable to feature, with knee and toe injuries respectively.
“No injuries from the game [against Chelsea] but also nobody recovered so no Mata, Jones, Smalling. They are out and still out,” added Mourinho. “And Wayne is the only one that is possible, if it's possible.
“I cannot confirm now but the paparazzi that live in the Lowry Hotel, they can take the picture when we go to the hotel at six o'clock and see if Wayne is selected.
“I would like him to be selected, yes, I would like to have him as an option.”