Pogba, who captained United against the Swiss champions, limped off in the 3-0 win and some reports have suggested he could be out for 12 weeks with a muscle tear.
Mourinho, however, said those suggestions were not based on truth and that the nature of the injury would not be known until after the results of further scans.
“I don’t know if it is 12 weeks or 12 days, honestly,” the Portuguese said after United’s 4-0 win over Everton in the Premier League on Sunday.
”Any comment or any new rumour is totally wrong because we don’t know if it is 12 weeks or 12 days. The player was diagnosed initially after the match because of the conditions of the muscle and the bleeding.
”The decision was one more week to wait to see really clearly in the scans, that I mentioned, of the injury.
“Nobody in this club spoke about 12 days or 12 weeks. Not at all. In the hamstring, it’s a normal procedure and we wait a few more days. So it’s completely nonsense information.”