Cristiano Ronaldo is approaching his sixth World Cup as if it were his first, Portugal coach Roberto Martinez said on Tuesday, brushing aside questions about the 41-year-old's form.

"It's his sixth World Cup, but I can say that internally it seems to be his first World Cup in terms of intensity, in terms of emotional output, of how important it is for him to be prepared to lead the group," Martinez told a press conference ahead of Portugal's opener against DR Congo.

Ronaldo, a five-time Ballon d'Or winner, holds the record for most international goals — 143. But he hasn't scored in his last nine matches at major tournaments. Critics say he offers little defensively when the opposition has the ball.

Martinez dismissed those concerns. "He's an example and a reference for football," he said. "For all those children on the street who begin to feel the love for sport, following the example of Cristiano Ronaldo is wonderful."

Portugal are among the favourites to win the World Cup for the first time, with a generation of talent around Ronaldo. Bruno Fernandes, fresh from winning Premier League player of the year, is part of what many consider the strongest midfield in the tournament. Vitinha and Joao Neves recently won their second straight Champions League with Paris Saint-Germain. Bernardo Silva is set to join Real Madrid after nine trophy-laden years at Manchester City.

Fernandes said his first memory of a major tournament was watching a 19-year-old Ronaldo help Portugal reach the Euro 2004 final on home soil. "All of us in this national team we have grown up watching Cristiano Ronaldo play and for us it's such an honour to play next to him now in the same team," said the Manchester United captain. "We're all here to support him and to support Portugal to go as far as possible."

Portugal are in Group K alongside DR Congo, tournament debutants Uzbekistan, and Colombia. Martinez warned against looking past DR Congo after Spain were held 0-0 by Cape Verde in their opening match.

"We've got very little to win tomorrow from the outside. If you win against Congo, it's expected. If you win by one, it's a big problem. If you draw, it's a catastrophe. If you lose, this is the end of the world," Martinez said. "They come with no expectations, they're enjoying being here. We've seen incredible performances from teams like Qatar, Cape Verde, exemplary performances, and that shows you that there are no easy games in a World Cup."

Martinez also confirmed he'll leave his role after the World Cup when his contract expires. "My contract ends after the World Cup. This isn't news, this is just a fact," he said. "We're now focused on finishing the work that we've begun three-and-a-half years ago."

He added: "When I came to Portugal the focus was to try to win everything, but most importantly to prepare for the World Cup."

Portugal face DR Congo on Wednesday in their first group match.