The Czech defender praised the Real Madrid attacker, but insisted that he did not lose any sleep ahead of his side's encounter with 27-year-old on Thursday
The 25-year-old, who recently revealed that he is poised to join Werder Bremen, has played a leading role for his team in Poland and Ukraine as Czech Republic finished at the top of Group A.
Gebre Selassie conceded that Ronaldo is a better player than those he has faced so far in the tournament, but is refusing to let nerves get the best of him ahead of the match.
"Every match at the Euros is hard, it does not matter who you face," he told Mlada fronta Dnes. "Perhaps facing Ronaldo will be a bit more challenging for me.
"He is one of the best in the world, but I am not afraid. I will not step onto the pitch scared because Ronaldo is there.
"He is very fast, always trying to play one-on-one, and he creates a lot of chances."
Gebre Selassie then went on to say that he thinks Lionel Messi is the best player in the world.
"I saw Ronaldo in action against Netherlands and he played well," the Slovan Liberec man stated. "But I think Messi is better.
"It is hard to compare, as they are different players. But Portugal are not just about Ronaldo."