Newcastle boss Alan Pardew was awaiting news of skipper Fabricio Coloccini after it emerged he has suffered an injury on international duty.
The Argentina Football Association confirmed the 30-year-old defender has a hamstring problem and although he is staying with the squad for the time being, coach Alejandro Sabella has drafted in Leandro Desabato.
A statement of the AFA's official website, afa.org, said: "Fabricio Coloccini has a hamstring injury in the femoral biceps of his right leg. He will travel with the squad to continue treatment with the team doctor."
Argentina face Paraguay in Cordoba, Coloccini's home city, on Friday and then travel to Peru on Tuesday sitting in third place in the South American World Cup qualifying table, but just two points behind leaders Chile with a game in hand.
But of more concern to Pardew will be the 30-year-old's readiness to play at Everton on his return.
The Magpies face the Toffees at Goodison Park on Monday, September 17 with their defensive resources having been severely depleted during the opening weeks of the domestic season.
Ryan Taylor is facing months on the sidelines with a cruciate ligament injury, while James Perch missed the 1-1 draw with Aston Villa because of a neck problem and Danny Simpson limped out of that game after damaging a hamstring.