The Belgian, just seconds after picking up a deserved booking for a foul on Sergio Aguero, once again bundled over the Argentine before head-butting him to the floor.
Martin Atkinson duly reached for a red card and Fellaini, much to the anger of Man United supporters, will miss the next three games as a result.
But Mourinho, when asked about the incident, was surprisingly supportive of the Belgian in spite of what was a potentially damaging moment of stupidity.
“I spoke with Martin [Atkinson] and he said in his opinion it was a red card. I didn’t watch but I can guess it is a bit of red card and a bit of a very experienced, smart Argentinian player.”
The 54-year-old hasn’t held back with his public criticism of various first team members this season, with Luke Shaw and Anthony Martial serving as the most recent examples, but he chose his words carefully here when discussing the 29-year-old. But why?
Perhaps because Fellaini’s downfall, unlike the aforementioned pair, occurred as a result of caring just a bit too much – displaying a sense of raw passion in the heat of the moment.
But this was the wrong kind of passion: Fellaini should have directed his commitment to the cause more towards serving as a better source of supply to the likes of Marcus Rashford – and isolated figure in the second half – and less towards burying his head into Aguero.
The Argentine was unsurprisingly theatrical in response, yes, but any head-butt – especially just moments after picking up a booking – will merit a red card, and Fellaini only has himself to blame.