Armenian midfielder Henrikh Mkhitaryan and Manchester United boss Jose Mourinho were involved in a heated training ground bust-up following a video analysis session, according to ESPN.
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.
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.
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 directly, Mourinho hinted that other deserved to play more than the Armenia international.
Inter Milan are reportedly 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.