An account dedicated to the 33-year-old, called ‘teamvalencia25’, posted following United’s 0-0 draw at home to Valencia on Tuesday, saying: “I’m not even surprised about the outcome of this game.
“I always look forward to our games but recently Mourinho has made watching us a punishment. Something needs to change. It’s time for Mourinho to go.”
The post was liked by Valencia, but he has now said sorry via a post on Twitter, explaining: “Yesterday, I liked a post on Instagram without reading the text that accompanied the picture.
“These are not my views and I apologise for this. I am fully supportive of the manager and my team-mates. We are all giving our everything to improve the results.”
It is not the first time a United player has found themselves in trouble for their social media activity in recent weeks.
Paul Pogba was last week filmed by Sky Sports News cameras in a frosty exchange with Mourinho, who was heard to question the timing of a video the midfielder posted on Instagram.
United are currently on a run of four games without a win, and have not won at home since the opening day of the season, when they beat Leicester City 2-1 on August 10.
Following their goalless draw against Valencia, United’s players and Mourinho are at Carrington, their training ground, as they prepare to play Newcastle United on Saturday.
The players that played on Tuesday are undergoing a recovery session, while those who were not involved are taking part in regular training.