The news was delivered to Pogba and the rest of the players at United's Carrington training ground on Tuesday.
Pogba was not involved for United last night as they were humiliated by Derby in the Carabao Cup third round.
Having lost two of their opening three Premier League games of the season, Manchester United recovered some form to win three games on the spin.
"Modern players need to look in the mirror but the manager has to take responsibility".
Pogba was slammed by his manager during training and told he would never wear the captain's armband again, as he did not have the right temperament for the job.
"I'm not the manager, I can not say that, but obviously we should show more options of playing".
Mourinho added: "No fallout at all, no problem at all, just a decision that I don't have to explain".
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On Monday, Pogba tried to downplay the issues with Mourinho, tweeting: "Some people make polemic even from "good morning" to create drama".
"I particularly enjoy it when the players perform like they did", he said.
Jose Mourinho might insist that there is "no problem at all" with Paul Pogba but these images would suggest otherwise.
The 25-year-old was dispossessed in the move that led to Joao Moutinho's equaliser, with the midfielder saying afterwards that United should "attack, attack, attack".
And he got away with a few nervy moments at Old Trafford, as Derby pulled off a brilliant upset.
Derby drew level though in spectacular fashion after 59 minutes with a brilliant bending free-kick from Harry Wilson, the young Welsh winger on loan from Liverpool.
The loss to Derby means United have not won at home since beating Leicester City 2-1 in the opening match of the season, with the Red Devils tasting defeat against Tottenham and drawing with Wolves since.
Fellaini came to United's rescue five minutes into stoppage-time when the Belgian converted Diogo Dalot's cross with a close-range header, however that was only delaying Mourinho's misery.