Jose Mourinho has given Manchester United the green light to step up their interest in Benfica full-back Alex Grimaldo, according to reports in Portugal.

The left-back position has been a problem area for Mourinho since his arrival at Old Trafford with Ashley Young and Daley Blind currently sharing first-team duties in that position. Neither would appear to be a long-term solution for the Portuguese coach, however, with Luke Shaw's future at the club looking increasingly bleak.

United have been linked with a £50m move for Tottenham Hotspur left-back Danny Rose after he conceded over the summer he would be open to a move to a club willing to offer more than he currently earns in north London.

But in 22-year-old Grimaldo, another option has emerged. The Spaniard was one of Benfica's brightest performers in their 1-0 defeat to United at the Estadio de Luz in their Champions League group stage clash eight days ago, catching the eye of Mourinho. According to Portuguese daily Record, the United boss has now given the club the 'OK' to intensify their scouting of the left-back during his next few games and for them to step up their interest in the player ahead of a possible move.

Grimaldo is a product of Barcelona's famed La Masia academy and was at one point tipped to be Jordi Alba's long-term successor at the Nou Camp. While he left the club in 2015 in pursuit of more first-team opportunities, he has refused to close the door on a return to the Catalan giants.

Manchester City have also been credited with keen interest in the Spain Under-21 international with Pep Guardiola, who knows the player from his spell at the Nou Camp, impressed with his progress since moving to Portugal.

Guardiola had been weighing up a January move for Grimaldo until injury struck late last year, with the player revealing at the start of the summer his "pride" with being linked with a move to the Etihad Stadium and a reunion with his former manager.

While City instead opted to sign Benjamin Mendy as their new first-choice left back during the summer, a long-term knee injury which is expected to sideline him for six months has left Guardiola open to signing another full-back in January.