He told reporters: "For us it is the most important match of our lives. The most important thing is not to lose.”
Poland coach Franciszek Smuda echoed his captain's thoughts and highlighted Greece's defensive strength as a potential problem for the curtain-raiser.
"Obviously we would prefer to win," he added. "But it is an opening game, and a tie would mean we remain in the race, because then we would still have two games we can win.
"Their defence is great. They play perfectly in defence. Their defence is a big challenge for us."
Poland finished their pre-tournament warm-up games with a 4-0 victory over Andorra on Saturday.