The Argentine defender, 26, ceased relations with his former representative two months ago, believing that working with Mendes' agency Gestifute would give him a better chance of securing a big-money move to the Premier League.
It wouldn't be the first time that a player has turned to Mendes to secure a transfer to United, with Nani's former agent Ana Almeida claiming he was still contracted to her when Mendes set-up his move to the Old Trafford club in 2007.
Bebe's agent Gonçalo Reis also made the same allegations just days before his former client agreed a £7.5million deal in Manchester in 2010.
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