Mkhitaryan, 28, has been absent from seven of United's last eight matchday squads and sources at Old Trafford have confirmed that the former Borussia Dortmund midfielder angered Mourinho by disagreeing with the manager's assessment of his contribution during a substitute appearance against Brighton on November 25.
Tony Pulis is no longer around to spar with, having been dismissed and replaced by Alan Pardew, but Mourinho made it clear the Welshman's legacy is still strong at the Hawthorns.
"I think for the right price", said Mourinho, when asked if he would listen to offers in such circumstances.
"But, at that time, even when I wasn't playing, I always had a smile on my face because if I would be sad or if I would be mad, nothing would help me".
Sources told ESPN FC in September that Mourinho was unhappy with Mkhitaryan's contribution against United's top-six rivals, but the player appeared to have overcome his manager's reservations by making an impressive start to the season with two goals and five assists in all competitions.
It was just a second goal in 10 Premier League outings for the Belgian and came after a conspicuously disappointing performance against City.
Mourinho has until 6 p.m. on Monday to explain to the Football Association comments made before the derby that City commit "tactical fouls".
"I'm not acting to the cameras or the fans. I was sure that my time would come and I would have one more chance". Bournemouth was a hard match and we coped with it, we did our work.
"If you score a goal in the last minute that gives you the victory in the last minute then yes. you lose your balance and you don't control your emotion: you react in an emotional way".
The Portuguese coach was asked at his news conference on Friday whether the prospect of an FA charge had put him in a position where he can not say anything at all before games. As you can imagine, I don't answer your question.
"What I like about the celebration was that he was still hurting from Sunday", Neville told The Debate on Sky Sports on Thursday night.