Ralf Rangnick has sent a warning to the Manchester United fans that booed Paul Pogba against Norwich City,
There was a poisonous atmosphere leading up to the Red Devils' 3-2 win over Dean Smith's men as a section of supporters staged a protest against the Glazer family outside Old Trafford.
And that toxicity spilled over into the stadium as they took aim at Pogba when he was replaced by Marcus Rashford with 15 minutes left. Supporters jeered the Frenchman with his future hanging in the balance.
There were also ironic cheers from large sections of the home crowd as "f*** off Pogba" chants came from the stands.
Pogba is set to be a free agent in the summer with the likelihood that he will leave the Red Devils after his second unconvincing spell at the club.
But interim boss Rangnick has defended his player and insists fans shouldn't be targeting individual players.
He said after the match: "I didn't hear, but I was told after the game. I can totally understand the fans being frustrated, but I don't think they should be targeting players individually. This is not right or fair."
The boos, aimed in Pogba's direction, continued after the final whistle as the players made their way off the pitch - prompting a reaction from Pogba. The midfielder was spotted cupping his ears in the direction of the fans.
Cristiano Ronaldo came to the rescue for United once again with an impressive hattrick against Norwich. The Portugal star fired Rangnick's side into a 2-0 lead in the first half before the Canaries got back on level terms.
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Ronaldo had the final say, however, scoring the winning goal in the second half to seal a 3-2 victory. But Rangnicks has warned United that they can't keep relying on the talisman.
He added: "We should not only rely on him. We played well at times but we sometimes slowed the game down and didn't make use of overlap situations on the wing. Defensively I was not happy at all."
"Like against Tottenham, Ronaldo was very crucial. They weren't easy goals, it was just outstanding.
"After we scored our second goal we should have made life easier for ourselves but we didn't. We lost our structure and weren't aggressive enough. It's about being clever and smart. All of a sudden it was 2-2 and David de Gea kept us in the game. But we definitely have to raise our play."