The France international has been forced to sit out the FA Cup fifth-round clash due to illness, with youngster Ethan Hamilton added to the squad in his place .
Pogba's absence comes just 24 hours after Mourinho said he would start the match as he hit back at "lies" concerning the midfielder's alleged unhappiness with life at Old Trafford.
Mourinho revealed he found out from United's medical staff early on Saturday that Pogba would not be available but insists he will not concern himself with the 24-year-old's absence until after the match.
"This morning, I was told by the doctor," Mourinho told BT Sport when asked when he learned Pogba was ill.
Asked whether it is a serious problem, he replied: "I don't know and, honestly, I don't care. I focus just on the game since the moment I knew Paul cannot play.
"I will think about Paul after the match, not now."
Pogba had earlier tweeted to confirm he had been advised to miss the match, saying: "Gutted I won't be at Huddersfield but I need to get better."
Gutted I won’t be at Huddersfield but I need to get better. Come on United 👊🏾 @ManUtd— Paul Pogba (@paulpogba) February 17, 2018
Earlier in the day a statement on United’s official website read: “Manchester United midfielder Paul Pogba will miss the Emirates FA Cup tie at Huddersfield Town due to illness and, as a result, Academy prospect Ethan Hamilton has taken his place in the squad.
“The young and industrious Scottish midfielder has impressed during his seven UEFA Youth League appearances this campaign, scoring one goal for Nicky Butt’s exciting team. Aged 19, he is also a regular in the club’s Under-23s team and featured on Friday night against Chelsea at Leigh Sports Village.
“This is Hamilton’s first inclusion in a first-team squad and we can confirm the youngster will wear the no.48 shirt at the John Smith’s Stadium, where the FA Cup fifth-round tie is scheduled.
“Ethan joined United when turning 16 after playing for Hutchison Vale, a local boys club the Reds have dealt with before when Darren Fletcher represented the Edinburgh-based youth team.”
Losing Pogba deals a substantial blow to United’s plans, but Hamilton will be relishing an opportunity to join the senior fold.
United’s Under-18s manager Kieran McKenna said of the youngster: “He is a fantastic character around the group and another one with a great training mentality every day. He's a hard worker who wants to get better and develop himself.
“He's a really solid player for the group as well as being a good talent. With his attitude, it could certainly carry him very far in his career.”
United, who are looking to respond to last week's shock Premier League defeat to Newcastle United, beat Huddersfield 2-0 at Old Trafford on February 3 but lost the away meeting 2-1 back in October.