Marek Jankulovski, Vaclav Sverkos and Libor Sionko have admitted that Czech Republic will have to raise their game to challenge Portugal on Wednesday.
The Czechs were less than convincing as they made a winning start to their Euro 2008 campaign against Switzerland on Saturday.
Portugal were impressive as they defeated Turkey 2-0 with Manchester United winger Cristiano Ronaldo keeping up his good form.
However, Jankulovski is aware that Portugal are not a one-man team and feels Czech Republic will also have to be wary of several other players.
"Ronaldo is not alone," said the defender. "Everybody talks about Ronaldo, but they have a number of dangerous players. Deco stars in the midfield, (Nuno) Gomes is dangerous up front, as well as Simao (Sabrosa) and (Ricardo) Quaresma.
"I saw a fantastic team (against Turkey). They have all excellent skills. Their attack is a great force."
Sverkos, who scored the winning goal against Switzerland, believes Portugal have the quality to go on and win the tournament.
"The Portuguese are one of the favourites," said the striker. "They have many players from top European clubs. You could hardly find a tougher opponent."
Sionko is looking forward to testing himself against Portugal but concedes that it will be difficult to pick up three more points.
"Portugal are in a different class than Switzerland," said Sionko. "We have to improve a great deal."
Captain Tomas Ujfalusi added: "The key is not to concede a goal. We have to be focused and convert any little chance we can get."