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 Nov. 25.

Mourinho was unhappy with Mkhitaryan's defensive work rate and a mistake made by the player, singling the Armenian international out for criticism in front of the rest of the first-team squad.

Mkhitaryan responded to his manager's remarks, with the player continuing to debate Mourinho's assessment of his performance in the corridor outside the analysis suite at Carrington.

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.

However, Mourinho was unimpressed by Mkhitaryan's performance against Chelsea at Stamford Bridge at the beginning of November and has not selected him to start since.

When asked on Wednesday why Mkhitaryan had not been in his plans recently, Mourinho said: "I can only have six [outfield] players on the bench and I try to have some balance on the bench -- I had two defenders and [Daley] Blind who can play in different areas. I had Ashley Young to cover me all of the wing and the wing-back position.

"I had [Ander] Herrera as a midfield player, Zlatan [Ibrahimovic] as a striker and Marcus [Rashford] as a second striker and winger. I played [Anthony] Martial, [Juan] Mata and [Jesse] Lingard in the team. To have Micki means that I don't have one of them and, in this moment, I believe the other ones they deserve [the chance to play]."

Inter Milan are keen to sign Mkhitaryan, who signed for United in July 2016, and could offer Portugal midfielder Joao Mario in an effort to negotiate a deal when the transfer window opens next month.