Faced with elimination from the tournament, Greece managed to beat Russia 1-0 in their last Group A game on Saturday and squeeze into the last eight. Santos said Monday that the absolute need to win that match had helped his players overcome their earlier lapses in concentration.
"I think knockout games are good for us because the players concentrate from the start of the game. When it's life-and-death, all or nothing, that has been an advantage for us," Santos told a news conference.
That said, Greece has plenty of respect for a Germany side that won all three of its matches in Group B.
"Germany's quality is without question, a team built over time that we all know well ... They are an excellent team with an excellent coach," Santos said, before adding a frank assessment of his own side.
"We know that we're not the best team in the world. But every opponent we have will have to sweat blood to get past us."
Greece will be missing two first-team regulars for Friday's game in Gdansk.
Playmaker and scorer of the decisive goal against Russia, Giorgos Karagounis, is suspended, while central defender Avraam Papadopoulos is out of the tournament due to injury.
Karagounis could be replaced by midfielder Grigoris Makos, who said that the Russia win had settled the team after two slow starts in the group.
"We've pulled off a big achievement so the pressure is off us," the 25-year-old said after training Monday. "We had been expecting the Germans to top the group. They are a great side so it was enjoyable to watch them play. Now that we are up against them, we will be looking a bit more carefully."
For midfield partner Yiannis Maniatis, the motivation is not just in beating Germany to advance to the semifinals, but also in giving people in hard-pressed Greece something to celebrate.
"We see this game totally in football terms," Maniatis said. "But it's important to make Greeks happy. Honestly that's all we want to do ... people are not having the best of times at home, and it was really great to see people out on the streets celebrating after the Russia game. We want to do that again."
Maniatis is due to get married on July 1 — the day of the Euro 2012 final — and he joked with reporters: "Maybe we'll have to move that date back a week."
Friday's game between Greece and Germany will be played amid a wave of resentment among many Greeks in the crisis-hit country over harsh bailout terms, which are backed by lead rescue creditor Germany.
Pro-bailout conservatives in Greece won a narrow victory Sunday in bitterly contested general elections.