Although the central defender still has more than two years remaining on his contract, the uncertainty over his desire to return to Argentina has not dissipated during the season.
Pardew said: "I have not had that conversation with Colo for a while, or about prolonging his contract. I am not really worried about it at this stage but obviously it is a conversation that I will have Colo and we will pick the right decision for the club.
"What might be right for him might not be right for the club but I am hoping we both make the same decision because I want him to stay. I think he is an essential part of this team. He is one of my most important players.
"I don't see anything to give me cause for alarm if I am honest. His mentality for the game will never change. He is quite calm. He enters the game to be the best player and most of the time, he is."
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