Defender Ruben Dias will miss Portugal's World Cup opener against the Democratic Republic of Congo on Wednesday.
"I think the preparation was perfect for everyone. Only Ruben Dias is not 100% for tomorrow so no, he's not fit to play. It's not the moment to take risks," coach Roberto Martínez said in a news conference on Tuesday.
"We did the medical checks, everything is structurally fine, we just need to avoid taking risks. Medically, we need him to be 100%."
Dias suffered an injury during the tune-up match against Nigeria ahead of the tournament.
Asked whether he regretted not naming another centre back, Martínez said: "No, I don't regret it, because we have three centre backs. Ruben Dias is doing well, but now we need to manage his. And then we have players who can also play in the centre back positions.
"The versatility of our group is better than trying to bring in a new player who doesn't have experience at the national team level and who doesn't have a clear understanding of what we're working on."
Portugal arrived at the tournament as one of the top favourites for the title and their top star Cristiano Ronaldo is set to equal Argentina's Lionel Messi as the player with most World Cup appearances (six).
Messi reached the mark as he started the match against Algeria on Tuesday.
"Cristiano once again is an example and a reference for football, for all those young footballers, or boys and girls who are beginning to feel the love for the sport," Martínez said.
"It's his sixth World Cup, but I can say that, internally, it feels like his first. In terms of intensity, emotional strength, how important it is for him to be prepared to help the team. And within the national team, he's a vital player because he's the finisher, the player who has those movements that can open up spaces for other players in our attacking game."
