The France star lasted just a handful of minutes on his debut as Red Devils captain before he was forced out of the action.
Pogba appeared to sustain a hamstring injury, and was replaced by Marouane Fellaini, who went on to open the scoring in a 3-0 win for the hosts.
And while medical reports are yet to determine the severity of the injury suffered on Tuesday, Mourinho was quick to point out other options for the weekend's Premier League clash should Pogba be ruled out.
"It looks for me too [like a hamstring injury] but I haven't spoken yet to the medical department," Mourinho said after the final whistle.
"Squads are for this, squads are for injuries, squads are for suspensions. We don't cry with injuries. So if no Paul for Sunday, we have [Ander] Herrera, we have [Michael] Carrick, we have Fellaini and we have [Nemanja] Matic."
"I just know from experience it's a muscular injury. In my experience, muscular injury stops you from playing for a few weeks, I think."