Greece head coach Fernando Santos rued his side's awful start as they slumped to a 2-1 defeat at the hands of the Czech Republic.
The 2004 European Champions know now they will have to beat Group A favourites Russia in their final game to advance to the quarter-finals in the competition.
The Greeks came into the game full of confidence after clawing back for a 1-1 draw in their opening match against Poland, but they could not overcome the loss of the two defenders - Avraam Papadopoulos and Sokrakis Papastathopoulos - who had anchored a usually stingy defence.
The Czechs took a 2-0 lead inside six minutes thanks to goals from Petr Jiracek and Vaclav Pilar.
Substitute Fanis Gekas got a goal back for Greece after half-time following a terrible error from goalkeeper Petr Cech but the Czechs held out.
And Santos claimed the Czechs had taken advantage of his side's makeshift defence.
"It was a game which started really badly for us," admitted the Portuguese coach.
"At the start we conceded two goals, although we had been warned that they would start quickly. We knew they would put pressure on us but we failed to respond.
"The Greek defence has only conceded four goals in 10 competitive game and now we have conceded three in just two games.
"Unfortunately the first 10 minutes really cost us.
"It was difficult to come back, we did everything possible to get an equaliser but we didn't make it."
Greece also had a first-half header by Giorgos Fotakis incorrectly ruled out for offside, but Santos did not want to cite that solitary moment as the reason for his side's defeat.
He said: "The truth is from my point of view it was difficult to say if it was offside or not. I wouldn't like to comment on that, but if it was a goal and it didn't count then obviously I think it was wrong."
Santos also confirmed that the injury suffered by goalkeeper Kostas Chalkias during the first half was a minor muscle problem.