The footage emerged just over 12 hours after they were dumped out of the Carabao Cup on penalties by Sky Bet Championship outfit Derby.
United sit seventh in the standings after six games, with 50% of those results being victories.
Speculation surrounded the future of the current boss after successive defeats to Tottenham and Brighton, but his side responded with victories over Burnley and Watford.
Mourinho recently stripped the midfielder of the vice-captaincy at the club, but denied that there was a rift between the two.
Despite being rested for the third-round tie, the 25-year-old remained a hot topic as it was claimed in the build-up that Mourinho had told the World Cup winner that he would not captain United again in front of the squad.
The video shows Pogba running onto the training pitch at the beginning of the session, shaking hands with team-mates and coaching staff.
He then stops after Mourinho says something to him. The pair continue to exchange words as they walk away, with neither looking happy with what was being discussed.
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