Sky Sports showed footage of Pogba joining training with his team-mates on Wednesday morning, including a seemingly terse exchange between the pair.

The 25-year-old shook hands with coach Michael Carrick and another United employee, before looking taken aback by something Mourinho said.

Pogba was then seen having an apparently exasperated discussion with the manager.

Despite being rested for the Derby clash, Pogba 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.

Asked about those reports, Mourinho told Sky Sports: "The only truth is that I made the decision of Paul not to be the second captain any more but no fall-out, no problems at all.

"The same person that decides that Paul is not the second captain anymore is the same person who decides that Paul was the second captain. Myself. I am the manager, I can make these decisions.

"No fall-out at all, no problems at all, just one decision that I don't have to explain."

Sources close to the club have not been surprised by the latest development, which will only increase speculation as to whether Pogba will stay at Old Trafford.

The France international captained the side in the Premier League openers against Leicester and Brighton in the absence of Antonio Valencia, just as he did in last week's Champions League win at Young Boys.

Pogba scored two and set up the other in the 3-0 victory in Switzerland, only to under-perform on Saturday's return to league action against Wolves.

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".

Those comments are said to have got under Mourinho's skin, but it is reported that Pogba's desire to leave Old Trafford for Barcelona was behind the decision to strip him of the vice-captaincy.

The pair's strained relationship is in stark contrast to the one between the Portuguese and Frank Lampard during their successful time together at Chelsea.

"I think he actually said that before the penalties, but I appreciate it.

"Jose was very welcoming as a whole. We obviously know each other, and he came and spoke to me before, we spoke during and afterwards. It was an honour for me to go up against him."

United paid for their failure to build on Juan Mata's early opener on Tuesday, with Harry Wilson scoring an exceptional free-kick and substitute Jack Marriott directing home either side of Sergio Romero's sending off for handling outside the box.

Marouane Fellaini's stoppage-time goal secured a 2-2 draw that took the third-round tie to penalties, with the spot-kick success giving Lampard the most memorable win of his short managerial career.

"I think I need time (to digest it)," the former England midfielder added.

"It was special – a special performance. To come to Manchester United and not to just nick one, but I think to play the way we played, doing all the things we have been working towards in a short space of time.

"To do it on this stage against this team full of top players with our squad which has some younger boys in it as well – the players were immense. What a night for the club to come here and do that."

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