Before the European Championship, Cristiano Ronaldo probably didn't count Denmark's second-string goalkeeper among the obstacles standing between him and an elusive trophy with Portugal.
But Stephan Andersen's clean sheet against the World Cup runner-up Netherlands is cause for concern for a Portuguese squad which lost its tournament opener to Germany 1-0.
"It's only by scoring we'll be able to win, but we'll have to be cautious because Denmark has shown that it can play well and score," said Nani, Portugal's second-biggest star after Ronaldo.
Andersen played a crucial role in Denmark's surprise 1-0 victory over the Netherlands, his first-half giveaway to Arjen Robben the only blunder in an otherwise spotless performance. The post saved him that time.
"There is no doubt that the match was the highlight of my career," Andersen told The Associated Press. "They have a lot of strong offensive forces in (Robin) van Persie, Robben and (Klaas-Jan) Huntelaar. So it was, of course, pretty nice to have a clean sheet."
The 30-year-old Dane, who plays for Evian in the French league, got the nod from Denmark coach Morten Olsen after first-choice keeper Thomas Sorensen was injured in a Euro 2012 warm-up match against Brazil.
Olsen was impressed by Andersen's flurry of saves against the Dutch.
"Fantastic. He lived up to our expectations," Olsen told The Associated Press on Monday. "I have to say that whenever Thomas Sorensen has been injured before, Stephan and (third-choice goalkeeper) Anders Lindegaard, who is also here, have done a fantastic job. We have super goalkeepers."
That's something Olsen's team has in common with the Danish squad that won the European Championship in 1992. Guarding Denmark's goal back then was Peter Schmeichel, considered one of the greatest goalkeepers ever.
His son Kasper is now one of Olsen's backup goalkeepers, a late addition to the squad after Sorensen's injury.
Portugal may have the bigger names, but it has beaten Denmark only once in the past five matches. The teams were in the same qualifying group for Euro 2012 and the 2010 World Cup. Denmark finished top of the group both times.
"They've shown us in previous games that they've got dangerous players," Nani said.
Their most recent encounter was in their final qualifier for Euro 2012 in Copenhagen, where Denmark won 2-1, securing the group victory and sending Portugal to the playoffs.
Ronaldo saved face for Portugal in stoppage time with a goal from a 30-meter free kick. While Sorensen was between the posts that night, Andersen said he'd rather not be put to a similar test by the Real Madrid forward on Wednesday.
"It is difficult to prepare yourself because he has a very special kick and he hits the ball in a way that makes it wobble and dip very late," Andersen said. "The best we can do is to avoid free kicks outside the area."
Despite Denmark's perfect start to the tournament, Andersen insisted Portugal should be seen as the favorite in the Group B match in Lviv, Ukraine.
"We still look at ourselves as underdogs," Andersen said. "That's what we were before the match (against the Netherlands) and that's what we'll be in the next two matches. It's a role that we don't mind."