After being sent for a scan on the problem, Pogba is now expected to be sidelined for a minimum of four weeks, and more realistically, six weeks.
Mourinho has also put the complete blame of Pogba's injury on the player himself, as a effect of not listening to the medical advice over what is a "long-standing issue".
After the match, Mourinho told MUTV: "I don't know (about the severity)".
"So for me, it's simple and objective: He's not playing this weekend".
This blooper reel from SpaceX's rocket tests is explosively entertaining
One of the best ways to do that, the company figured, was to stop throwing away the first stages of its rockets. SpaceX has put together a bloopers video showing "How NOT to land an orbital rocket booster".
Mourinho will need Herrera to cover for the injured Frenchman and this is the opportunity the fan favourite has been waiting for. I just know from experience it's a muscular injury. I just know it's a hamstring problem.
Pogba missed three games with a similar injury last season, and The Sun report that he "was given clear instructions by United medical staff to prevent any recurrence". We lost important players last season and we were not crying or getting excuses.
Sunday's match will see Rooney return to Old Trafford for the first time since leaving Manchester United for Everton in July.
"Sometimes in England the word "legend" comes too easy".
The former Athletic star has less than a year remaining on his United contract, and James Ducker of the Daily Telegraph reported in July the Red Devils were working on tying him to a new long-term deal.
Apparently though the France midfielder instead opted to seek treatment from an external personal trainer and Mourinho and the United medics feel that has "made the midfielder far more vulnerable to injury".