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The Argentina captain cut a remarkably relaxed figure ahead of the game against Saudi Arabia in Doha, repeatedly stressing how much he is enjoying his football as his glittering career enters its final chapters.
Messi caused alarm over the weekend by failing to show for the section of training open to the media, but he was quick to rule out any injury concerns."I am feeling very well physically, I'm in good condition. I come here in really good form, both personally and physically. I have no issues whatsoever.
"There were rumours about missing part of training, but no, it was just a precaution, nothing out of the ordinary."
Messi accepts this will be his last realistic shot at World Cup glory, but Argentina's Copa America win last year has lifted an element of pressure and the 35 year-old is determined to depart the global international stage with a smile.
"I don’t know if it’s the best moment in my career but I feel really well and perhaps a bit more mature, always trying to give my best and enjoying everything," Messi said. "I think I’m enjoying it much more now.
"Before I didn’t think about that, I just wanted to play. Now I am trying to enjoy it, but when you play every three days it's sometimes tough.
"Age makes you see things differently, and maybe give more importance to small details. Perhaps before I didn't do that. Now I try to focus on the details and enjoying it is more important than everything else."
The unusual timing of this World Cup has meant a different build-up, but Messi says the pre-tournament nerves remain the same.
"It is different, we usually play the World Cup at the end of the season and we normally have a whole month to prepare," he said.
"Now it's completely different. We've had little time to prepare, but we knew this was the situation. It's always special.
"We expect a tough game, we are aware of this because it's the beginning of the World Cup. We will have to deal with the nerves the best way we can."
Argentina coach Lionel Scaloni also pinpointed his side's 2021 Copa triumph in Brazil – their first major title in 28 years – as a key factor in why they have arrived in Qatar with a quiet confidence.
He said: "The reality is we now play in a much more calm way, we don’t have that weight on our shoulders.
"We are always calm when we go on the pitch and like to feel that freedom. And then it comes down to details. Emotionally we are far more assured and that allows us to play our football.
"But a nation like Argentina always has pressure and if the results are not the best it's obvious that we have criticism.
"We knew about the journey we had to take and we need to keep doing that. We think that’s the best way to do it. We respect the other teams, but we are here to be competitive."