Goalkeeper Orestis Karnezis will be given until Sunday morning to prove his fitness before Greece's round of 16 match versus Costa Rica.
Greece coach Fernando Santos confirmed on Saturday he remains unsure about Karnezis' prospects for Sunday's game in Recife.
Karnezis was substituted in the first half of Greece's vital 2-1 win over Ivory Coast to reach the knockout stages of the FIFA World Cup and while he trained on Saturday, Santos was unwilling to promise anything regarding the Granada gloveman.
"We don't know yet whether Orestis Karnezis is fit," the Portuguese coach said.
"He trained today and he didn't present many problems but we still have almost 24 hours to analyse the situation. He will only play if he is a hundred per cent, if the medical department ensure that he has is ready to play the match.
"If the game was now, I would say he has a huge probability, but until tomorrow, it is a difficult situation to analyse. We will decide this matter in the morning."
It also remains unclear whether Panagiotis Kone (hamstring) will play, after the defensive midfielder lasted just 11 minutes against Ivory Coast.
Greece advanced to the round of 16 of a World Cup for the first time ever last week, when Giorgos Samaras won and converted a penalty in second-half stoppage time to eliminate Ivory Coast.
The win was celebrated wildly in Greece, which continues to struggle with serious economic problems and defender Vasilis Torosidis, who has started all three of his country's games so far, wants to give his compatriots something more to be happy about at the Itaipava Arena Pernambuco.
"We saw it so clearly that it (the win) gave joy to our people," Torosidis said.
"People took to the streets and there's no doubt our country is experiencing a difficult moment. All the players, the manager, the technical team have one more incentive to play well, to make people happy because of the situation in Greece.
"But we don't want to stop here. We achieved something four-five days ago and now we want to give even more joy to our people."