Manchester United manager Jose Mourinho has lashed out at Paul Pogba's critics, claiming the France midfield "does not give an ass" what they think and that envy is fuelling his detractors. 

Pogba's indifferent performances have been heavily scrutinised since he returned to Old Trafford for a world-record £89.3million fee from Juventus in August.

The critics were out in force again on Monday as Pogba underwhelmed in United's 1-0 FA Cup defeat at Chelsea, with his international team-mate N'Golo Kante shining for Antonio Conte's men.

But Mourinho defended Pogba in the aftermath of that game and continued to back the midfielder ahead of Thursday's Europa League second-round tie against Rostov.

"I feel that the world is losing values and we all know that and envy is coming into certain levels that I am scared with," Mourinho said of Pogba, who turned 24 on Wednesday, at a pre-match news conference.

"It is not Paul's fault that he gets 10 times the money that some very good players get. It is not Paul's fault that some fans are in trouble and need every penny to survive and that he is a multi-millionaire.

"He needs respect, his family deserve respect. He is from a working family, a family with three boys and I am sure they need a lot of food on their table each day because they are all giants, so I'm sure that the mum and dad had to work hard for many, many years for them.

"A kid that comes to Manchester as a teen to fight for his career here and was not afraid to work for a better life. He reached the top of the world, nobody gave him anything.

"I am very happy with Paul. The club is very happy with Paul and I think the good thing is because of his personality he does not listen to what people say. He does not give an ass about criticism."