The 24-year-old led Manchester United out as captain for the first time on Tuesday night for their Champions League opener against Basel.
But the France international lasted just 19 minutes of the 3-0 Group A win before a hamstring complaint forced him off.
Pogba left Old Trafford on crutches and has undergone scans.
But Mourinho insists no definitive prognosis has been made on the midfielder’s return date amid talk of a three-month lay-off.
“I don’t know if it is 12 weeks or 12 days,” the United boss said after tonight’s 4-0 defeat of Everton.
“Honestly, so any comment, any rumour is totally wrong, because we do not 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 and to see really clearly in the scans the dimension of the injury.
“And nobody in the club spoke about 12 days or 12 weeks. Not at all.
“It’s a muscular injury in the hamstring, but we have a normal procedure and wait a few more days, so it’s completely nonsense information.”