Pogba, who turned 25 this week, arrived back at Old Trafford in 2016 for a then world-record £89.3m (R1.5b) deal but has struggled to make the required impact expected of him this season.
The France international has looked lacklustre in recent weeks and his lack of work-rate was viciously exposed in the 2-1 UEFA Champions League defeat to Sevilla on Wednesday.
A return of three goals and 10 assists in 27 games has seen the supremely talented France international drop to the bench under Mourinho in recent weeks, despite being held in high regard as the club's record signing.
"Paul, I'll give him a little bit of advice -- change attitude a bit," 1998 World Cup winner Emmanuel Petit said, as quoted by ESPN FC.
"He should stop making it a Mourinho-Pogba duel, because the club of Manchester United is much more important than those two guys.
"Right now, he's making it personal and you can clearly see that on the pitch as he is sending out a lot of negative signals.
"It gets tiresome when you're sulking permanently."