The absence of Greece captain Giorgos Karagounis will be hard to fill, according to manager Fernando Santos.Karagounis was booked for diving in the 1-0 win over Russia which earned Greece second place in Group A.
The yellow card rules him out of Friday's last-eight meeting with Germany, a decision that looked harsh with replays showing the midfielder should not have been booked for diving after he had been clipped by Sergei Ignashevich.
"Karagounis is a very important player for us, he is our captain, he is experienced and for sure his presence is felt by the players," Santos said.
"It is very sad for us that he will not play because the card he was shown was not justified, and that is not fair for the whole team.
"I said yesterday and I repeat today that I am the coach and I have to find the solution to who is going to play in his place, in order for the team to be at their best.
"I am 100 percent sure that whoever will play will do the same job, he will be as effective."
"At this moment we are at another level, we are not playing in the first stage, we are in the quarter-final. All the matches will be difficult. From now on all the games are knock-out matches, even if it is 90 minutes or extra-time or a penalty shoot-out, everything is possible, we have our chances."
Karagounis, who scored the winner against Russia, believes the delight of reaching the quarter-finals rivals that of winning Euro 2004.
"We did not give up. We can compare this to our cherished moments in Portugal in 2004," he said.
"We believed all day that we would not return to Athens (after the group phase)," added Karagounis, who won a record-equalling 120th cap against Russia.
"We kept our promise to all. All Greeks can now celebrate. When we are united no one can stop us."