The French international missed Saturday's FA Cup win at Huddersfield through illness, with Mourinho admitting post-match that he doesn't know whether his star man will be fit for Wednesday's game.
"I don’t know. Now is the time to think about Paul, to know what happened, why he didn’t feel good enough to play, can he play or be available to help us on Wednesday," Mourinho said after the game when asked if Pogbe would be fit.
Pogba reportedly demanded this week that he play on the left of a 4-3-3 system in order to get back to his best and Mourinho revealed that he was set to play there, until his late withdrawal.
"Yesterday he was working normally with us. We prepared for the game, we gave the last touches in the tactical play, we gave the last touches on the set-plays and I told the players the team," the Portuguese explained.
"He was in the team but this morning he was not feeling right to play. Then I have to prepare a new team. So he’s ill and now we have to wait to see what is going on.
"Just as curiosity, it was Michael Carrick who replaced Paul. Paul was going to play on the left side as a No 8 in a 4-3-3.
"Then when the doctor told me Paul was not feeling good to play. We moved Matic to the left which is not his favourite position and Michael to his traditional No.6."