The Black Cats have agreed a fee with Velez Sarsfield for the 21-year-old right-back, but are yet to finalise the deal, and it emerged in South America that personal terms could be the problem. Velez vice-president Julio Baldomar told TyC Sports: "The player and his agent say that the offer from Sunderland isn't sufficient - not the transfer fee, because the player will take 15 per cent, which is enough, but what they've offered him. They say that isn't it what they want. "It's the first time where we've arranged a transfer to a European club and after the player tells us that he wants them to offer more." Whether or not the interested parties can negotiate a way around the sticking point remains to be seen, but Baldomar admits a failure to do so could cause his club significant problems. He said: "If the player isn't transferred, we have to sit down with the board to see what the next step will be. "It's an exceptional case because generally when there appears an offer from Europe, the players is the first person who wants to go. Read more at: