Tuesday's long-awaited Champions League return came at a cost, with the 24-year-old only lasting 19 minutes of the 3-0 victory against Basle.
Pogba had been captaining United for the first time when he pulled up as he challenged for the ball
The France international left Old Trafford on crutches and Mourinho is unsure about his absence beyond Sunday's Premier League clash with Everton.
"I don't know, I just know that it's a muscular injury," the United boss said.
"He's obviously out for the weekend match
The weekend match is the only match that I'm thinking about
I don't think further than that.
"So, for me, it's just simple and objective: he's not playing this weekend."
Immediately after the Basle match, Mourinho spoke of his expectation that Pogba - one of the stars of the first few weeks of the season - faces a "few weeks" out
However long it ultimately is, the United boss has no doubt his players will step up to the plate
Michael Carrick, appointed captain in the summer, has yet to play a competitive minute this term, while Ander Herrera - left out of the squad on Tuesday - and Marouane Fellaini offer alternatives.
"We have players and we have players waiting for an opportunity," Mourinho said.
"Because we have started the season really well and with one match per week, (with) no need of resting, (to make) changes, we were basically going with the same players.
"But there are good players more than ready to play, so, honestly, we miss Pogba, we need Pogba, but we have good players.
"Herrera, Fellaini, Carrick, they are waiting - they are waiting for a real chance to start matches and to play matches from the beginning, and they are ready.
"So this is also our way of thinking
We lost important players last season during the season and during crucial moments of the season and we were not crying or making excuses about that
That's just football.
"Squads are (there) to try to cope with these kind of situations and we know that for a few matches - I don't know how many, I really cannot tell you how many I expect - but we are going to play without Pogba a few matches."
Source : PA
Source: PA