Paul Pogba got up and left after Jack Marriott put Derby in front with five minutes remaining at Old Trafford.
Mourinho confirmed before kick-off on Tuesday night that Pogba was merely rested for the Carabao Cup third-round tie but much of the talk around the game focused on the pairs increasingly fractured relationship.
The night got off to the perfect start for United, though, as Juan Mata found the net in the 3rd minute but Harry Wilsons stunning free-kick followed by Marriotts 85th-minute effort gave Derby the advantage at the death.
Maroaune Fellaini took the game to a penalty shootout with a scrappy goal from close-range but Scott Carsons save to deny Phil Jones spot-kick sent Derby into the fourth round of the competition.
Jose Mourinho's last 4 days:
– Drew at home to Wolves
-Stripped Paul Pogba of captaincy
– Knocked out of EFL Cup to Derby
"Nimeenda ivi nakam "~Pogbapic.twitter.com/19R8upTB50
— Php Ninja (@kisugugu) September 25, 2018
How Pogba reacted to Marriotts 85th minute goal…
Seen enough, Paul?
Wilson, who is on loan at Derby from Liverpool, predicted that the Rams could cause an upset at Old Trafford.
Ive played a 23s game there for Liverpool but not a first-team game, so Im really looking forward to going there and putting in a good performance, he said.
I think if we play the way we have in the past couple of games, we can go there and get a positive result.
I think these are the games everybody wants to play in, and well go into that game with a lot of confidence.