Defender Andreas Granqvist believes Portugal can be beaten but acknowledged that the Real Madrid forward has formidable pedigree.
The Seleccao were drawn against the Scandinavians in a playoff qualifier after both teams finished second in their qualifying group in what has been billed as a showdown between Zlatan Ibrahimovic and Ronaldo.
Ahead of the opening leg on Friday and the second game four days later, Granqvist has commended the Real Madrid attacker's talents but insisted that victory for Sweden is possible.
"We will not leave Ronaldo too much space," the 28-year-old, who plays for Russian side Krasnodar, told reporters. "If we can defend as a team, sticking together, I think we can succeed.
"A key thing will be to stay glued to him all the time so he does not have time to play. It is clear that this is one of the best players in the world and is currently in great shape. He scored a lot of goals for Real Madrid this season, both in the Champions League and La Liga."
The winner of the two-legged tie will feature in the World Cup next summer in Brazil.