Greece coach Fernando Santos called his players "brilliant" after they held on for nearly an hour after going down a man to earn a goalless draw against Japan.
Kostas Katsouranis received his second yellow card in the 38th minute but Japan were unable to break the Greek defence.
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"It affected the game fundamentally -- 11 versus 11 is different," Santos said. "I told my players that they have to work well defensively and stay compact and go on the counter attack. At some times, we were shooting off-target continuously. But my players were brilliant in terms of how they performed on the pitch.
"We lost Katsouranis, but we have other men."
Santos said he thought his team got off to a good start and could have earned all three points if not for Katsouranis' dismissal.
"The match was balanced until the sending off, which marked the beginning of a new phase of the game. This makes it tough on us," Santos said.
"Japan had a lot of ball possession and dominated the second half. We were good in terms of determination, courage and defense, but had difficulty finding the ball and going on the counter-attack."
"The second half was very tough for us. I want to congratulate the players because they played well after the red card. Had there been no red card, I felt that we could have won the game."
"We had difficulties in the attack. We were not getting there. We did well in the first half but not the second half."
Greece sit at the bottom of Group C and must beat Ivory Coast and hope Japan do not beat Colombia.
"Against Ivory Coast, there is no other solution but to win. We are depending on ourselves and Colombia versus Japan.
"We will have to play man-to-man against Ivory Coast and try to find spaces in the midfield. We must be brave and we must dare. The players will do their best in the next match to try to go against the individual qualities of the Ivory Coast players.
Santos also offered a plea to Colombia, who are already assured of a place in the group stage, saying, "Colombia, please don't let Japan win! As respectful as I am, that's all I can say."