The coach pledged that his side will learn from the errors committed on the first day of the tournament, otherwise they will be punished by Ronaldo and Co. on Thursday
Bilek's first game in a major competition ended in a 4-1 hammering at the hands of Dick Advocaat's side, but the Narodak bounced back to secure their place in the last eight as pool winners thanks to successive victories against Greece and co-hosts Poland.
But with Cristiano Ronaldo returning to form with a brace against Netherlands, Bilek insisted he will set up his side to be more conservative than in their first game of Euro 2012.
"We know Portugal have dangerous players in midfield and up front, such as Nani, Helder Postiga and Ronaldo," he told Uefa.com
"We have that in mind, and we'll adjust our tactics to be more defensive.
"We can't play like we did against Russia. We gave them space and they punished us. Nani and Ronaldo will punish us if we do the same thing again, and we don't want to repeat the first match."
Arsenal midfielder Tomas Rosicky missed the final group game with an Achilles problem, and faces a race against time to be fit after seeing a specialist back in Prague, but Bilek is confident that his team's ethic can see them through.
"During qualifying we put together a team," he said.
"We don't have any great stars, except for Tomas Rosicky and Petr Cech. The team spirit is excellent, and if we defeat Portugal it will be thanks to this team."
The former international midfielder also revealed that he is looking to repeat the heroics of the Czech side that defeated the Seleccao 1-0 at the same stage in Euro 96 thanks to Karel Poborsky's wonderful lob, before they were beaten by Oliver Bierhoff's golden goal in the final.
"The situation is similar, they are favourites" he said.
"They have strong individuals and a strong team, but if we repeat our performances from the previous two games, we have a chance of going through."
The game in Warsaw kicks off at 20:45CET.