Ronaldo is the obvious threat to Poland's chances of reaching the semi-finals, the Real Madrid star having scored two goals at the tournament - both against Hungary in the group stage - but Nawalka insists Fernando Santos' men have other dangerous players.
He said: "Portugal are a very tricky opponent with great potential. They have players who play at the highest level.
"I don't even want to mention Cristiano Ronaldo, he's one of the best players in the world and that says a lot about their team.
"But football is a team game, there is no team for whom one player decides the outcome of the match. I think Portugal present themselves very well as a whole team.
"For us we don't need to look only at Ronaldo but their other players as well.
"What is clear about them is how they recover possession, they attack very well, they are very dangerous and we are expecting a very difficult match, but we believe in ourselves, we look to control the game according to our gameplan.
"We are full of faith and optimism."
"Lewandowski is a very important player for our team," he said. "I am happy with his performances so far, he's playing for the team and he's fulfilling a very important role both as a captain and as a player on the pitch.
"He is in very good physical form and mental form, he's doing a great job for us and let's keep it that way.
"For me he's the best number nine in the world."
Nawalka was adamant Poland's progress to this stage had not come as a surprise to him and believes it is reward for the hard work they have put in.
"The fact that we have achieved the results we have at this competition is not a shock for us," he added. "We have been expecting that from the beginning.
"We have been making progress and we've been expecting this by playing a high level of football.
"We wanted to reach this tournament in the right form, the players have done amazing work in the qualifiers and when we were preparing for the tournament. It was a very important period for us, and you can see it [the results] now.
"For me as a coach it's very important that all the players work as a unit and are a team. I hope they will be helping each other and celebrating our successes together. We are working as a team, our team spirit is the foundation of what we are achieving here."