​Premier League giants, ​Manchester United will allow Chris Smalling to sign for AS Roma on a permanent basis, only if they are able to lure Kalidou Koulibaly from ​Napoli to Old Trafford in the summer.

Koulibaly, who is widely considered to be one of the best defenders in the world has long been linked with a move away from Italy with United said to be keen admirers of his style of play and a perfect player to shore up their backline.

As per ​La Gazzetta dello Sport, United would be willing to let Smalling sign for Roma on a permanent basis if they can secure the services of the Senegalese international, though they will face competition from other top clubs for his signature.

Smalling was sent to Roma last summer on a year-long loan as he was deemed surplus to requirements by manager, Ole Gunnar Solskjaer following the arrival of Harry Maguire for a world record transfer fee for a defender.

Smalling for his part has rejuvenetaed himself and has emerged as one of the best defenders in the Serie A and it has led to Roma wanting to sign him permanently - with the Englishman becoming a hit with the fans, with some even going on to give him the moniker of "Smalldini", in reference to the legendary, Paolo Maldini.