"I'd like to congratulate my players for all their effort. This was a difficult match, and they gave everything for this qualification," the Portuguese coach said.
He underlined that securing a berth in the last eight was highly symbolic for a country locked in a deep economic crisis, as well as having a personal edge for a squad who lost defender Avraam Papadopoulos to injury in their first match of the tournament.
"It goes without saying that we are very happy and very satisfied," he said. "We managed to give joy to Avraam and to all the Greeks. I think what we achieved was very important. This result was a result of the effort and decisiveness of all my players."
Santos said Greece would not let themselves give in to euphoria, however. "Tomorrow we have to clear our minds and keep our feet on the ground. Just because we won this game, it doesn't mean we are the best in the world," he said. "But just because we lost the previous match, it doesn't mean we are the worst. We know who we are."
Greece had come into the Russia match on the back of a 2-1 defeat against the Czech Republic, who also earned a quarter-finals berth on Saturday by beating tournament co-hosts Poland 1-0. The Greeks' EURO 2012 campaign had begun with a 1-1 draw with the Poles, where they showed their fighting spirit by battling back with ten men to equalise.