The attacker returned to Old Trafford last summer and has been in impressive scoring form this season, netting 14 times in 21 appearances in all competitions.
Man United's struggles have allegedly led to the Portuguese becoming unhappy at the club, though, with the forward regularly showing his frustration on the field.
The report claims that Barcelona could potentially be interested in signing the former Sporting Lisbon youngster, who has a contract at Old Trafford until June 2023.
Man United's chances of winning this season's Premier League are all but over due to their struggles in the first half of the campaign, but they are still chasing silverware in the FA Cup and Champions League. body check tags ::