The Red Devils scouts have been regular at Porto games, watching James Rodriguez and Eliaquim Mangala, but it appears the Brazilian defender also caught their attention.
Sir Alex Ferguson is searching for a long-term replacement for veteran defender Patrice Evra and Alex Sandro is one of the first names on his hit-list.
The 22-year-old has been making steady progress since joining the Dragons from Santos in the summer of 2011 and he has been one of club’s star performers this season.
Sandro scored one goal in 19 Primeira Liga matches, but also impressed in 6 Champions League fixtures.
The talented defender has earned 6 Brazil caps and he made another three appearances for the Under-23 side at the 2012 Summer Olympics.
Alex Sandro has a contract until June 2016 at Estadio do Dragao and is predicted a bright future in the game.