Paul Scholes erupts in X-rated social media post as Man United slip to disappointing West Ham draw

Amorim had attempted to explain his team selections last week, saying: “I see him as a starter like the other players.

"I just have to make a choice and then in the end, it's not been Kobbie.

"In the future, I don't know. Again, I always think the same thing with Casemiro.

"[He] was not playing and then he plays. I just want to win games. I don't care who is playing.”

But those assurances carried little weight for Scholes once Mainoo was left on the bench even as United tried, and failed, to protect a fragile 1-0 lead at Old Trafford.

The 51-year-old made his feelings unmistakably clear.

“Bulls**t,” he wrote on Instagram in response to Amorim’s comments.

“The kid is being ruined, not being played in a team that can't control a game of football.

"Hate seeing home grown players leave but it's probably best for him now, enough is enough.”

Scholes’ anger was fuelled by the sequence of substitutions that unfolded as United attempted to close out the contest.

Mason Mount, Manuel Ugarte, Patrick Dorgu, Leny Yoro and Lisandro Martinez were all introduced as United sank deeper, but Mainoo, arguably the most composed midfielder in the squad, remained unused.

United eventually conceded a late equaliser.

Pressed afterwards about the defensive nature of his changes, Amorim said he feared United would lose control of second balls in midfield.

When a reporter suggested Mainoo as the obvious attacking alternative, the United manager responded with a laugh - an exchange that only intensified supporters’ frustration.

Mainoo’s lack of involvement this season is stark.

He has played just 171 Premier League minutes, with his only start coming in United’s shock Carabao Cup defeat to Grimsby Town in August.

Last weekend at Selhurst Park, he appeared visibly annoyed when he was brought on deep into stoppage time to help protect a 2-1 lead over Crystal Palace.

The midfielder, who broke through two seasons ago and was widely tipped to become a long-term fixture in United’s engine room, now appears to be sliding backwards at precisely the stage when he should be accelerating.

Scholes is far from alone in feeling that the situation has become untenable.

A growing section of United’s fanbase share the belief that Mainoo may need to leave in order to develop properly. Napoli explored a move in the summer and are understood to be monitoring him again ahead of January, with sources in Italy convinced they can offer minutes that United currently cannot.