The Portugal boss also dismissed concerns about Ronaldo's explosive interview with Piers Morgan in which he criticised his club, Manchester United.

The player did not say anything derogatory about his national team, though he did receive a frosty reception from compatriot and United team-mate Bruno Fernandes when he arrived to prepare for the World Cup in Qatar, which begins on Monday (AEDT).

Santos said: "Ronaldo has gastritis and did not train today in order to recover and rest. It's a condition that doesn't help much as it affects the players a lot, they lose a lot of liquid, they weaken. He won't be ready for tomorrow, for sure."

Santos also denied that it was an excuse for Ronaldo to stay out of the limelight while the media continues to discuss his comments about the likes of United boss Erik ten Hag and the general state of the club he rejoined last year.

"[Ronaldo] didn't have to inform us about the interview," Santos said. "Isn't he free [to make his decisions]?

"What I'm interested in is what is being spoken about in our camp and not what is being said outside. We have to respect his decision.

"We have to respect the interview he gave. It has nothing to do with the national team."

Portugal begins its World Cup campaign against Ghana on 25 November, before also taking on Uruguay and South Korea in Group H.