The 31-year-old full back has less than six months remaining on his Barcelona contract, and will join up with Brazilian compatriots David Luiz, Marquinhos, Maxwell and Thiago Silva in the summer
The news will be a big blow to Manchester United boss Louis van Gaal, as signing a top right back is one of his biggest priorities this summer.
United are expected to now turn their attention to Southampton right back Nathaniel Clyne in the summer, according to the Mirror.
The England international has been an regular fixture in Ronald Koeman’s side this season, helping them to the best defensive record in the league having conceded only 20 goals.
Clyne has played all but two of Southampton’s Premier League games this term, and has won 57/125 tackles (46%).
As the stats below shows, Clyne would be an improvement over both Valencia and Rafael this season.