If Argentina are to become the first nation to successfully defend their World Cup crown since 1962 - and just the third ever - you can almost guarantee Lionel Messi will be at the centre of it. The 38-year-old is preparing for his sixth World Cup - which will be a joint record with Portugal's Cristiano Ronaldo and Mexico's Guillermo Ochoa - but it will be a very different Messi from the one who made his debut for Barcelona back in 2003.

Most players decline. The elite ones find ways to adapt. Ronaldo reinvented himself as a penalty-box predator when his pace went. Messi has not adapted to decline. He has adapted so he can dominate and stay ahead of a game that has always been chasing him. Since that 16-year-old made his Barca debut in a friendly against Jose Mourinho's Porto, playing on the right, dribbling and often cutting inside, Messi has reinvented himself at least five times to evolve into the player he is now for Argentina and Inter Miami.

When Ronaldinho, the then best and most recognisable player in the world, saw him train for the first time, he said "he will be the best". Two years later, in August 2005, Messi announced himself to the world in the Joan Gamper Trophy against Juventus. Fabio Capello, the Juventus manager, was so startled by the 18-year-old that he reportedly tried to sign him.

By the time Messi was 21, with Ronaldinho fading and the baton passing, then Barca manager Frank Rijkaard was clear about what the team needed from him. "Right in the centre of things," Rijkaard said. "The more he touches the ball, the better for the side." During the first months of Guardiola in charge in 2008, the right side of the pitch was the Argentine's corridor, his private road to goal.

The first time Guardiola decided to move Messi away from the wing was for defensive reasons. He did not track back and the full-back struggled. But the Catalan manager knew that Messi was always going to end up in the centre of operations. And the team would be built around his new position, for the biggest of stages and the biggest of moments.

The date: 2 May 2009. The place: Santiago Bernabeu Stadium, Madrid. La Liga game. Guardiola made a decision. He pulled Messi off the right wing and placed him at the tip of the forward formation - but without the job of a traditional striker. Samuel Eto'o went right, Thierry Henry went left, and Messi was told: drop, receive, decide. By full-time it was 6-2. The false nine was reborn.

It was nothing new. Gusztav Sebes' Hungary had dismantled England in their own backyard back in 1953, when in their 6–3 win over England he repeatedly dropped Nandor Hidegkuti into midfield, pulling centre-backs out of shape and creating space for Ferenc Puskas and Sandor Kocsis. Johann Cruyff, first under Rinus Michels, played a roaming forward role within the Total Football philosophy for the Netherlands.

At first, Messi became a problem without a solution. When he dropped between the lines, Madrid's centre-backs had to decide: follow him and leave a hole, or stay and give him lots of space. Neither option worked. Messi walked through the gap unchallenged. With Xavi, Andres Iniesta and Yaya Toure behind him and Henry and Eto'o stretching the defence wide, every decision the opposition made was the wrong one.

Guardiola repeated the experiment weeks later in the Champions League final against Manchester United. Messi scored with his head 20 minutes from time. Between 2011 and 2013, Messi scored 96 goals over 69 La Liga matches. The Ballon d'Or that had been handed to him in 2009 became a near-permanent fixture - he won it in 2010, 2011, 2012, 2015 and 2019 as well, and would eventually accumulate eight. The first arrived when he was 22. The most recent when he was 36.

"I didn't used to pay much attention to tactics," Messi told journalist Juan Pablo Varsky in 2024. "But with Guardiola I learned an enormous amount. I started to understand spaces, ball retention, how the game really works."

When Xavi left Barcelona in 2015, and Iniesta three years later, something shifted. Messi had always been the decisive player, now he was being asked to be the entire engine. The midfield that had been his safety net - the men who kept the ball moving and created the space he thrived in - was gone. For a period, Messi was expected to be Xavi, Iniesta and the goal scorer simultaneously. It was too much to ask of anyone. He handled it by evolving again.

The goal scorer and number 10, or false nine, became the 'enganche' (the hook) - dropping deeper, he was now the organiser, the man who initiated and often finished. Assists began to rival goals in his statistics. In the 2019-20 season, he registered 22 assists and 25 goals in 33 La Liga games. He returned to his goalscoring best in his last season with Barcelona (2020-21) with 30 goals and 11 assists from 35 La Liga games. But his first season at Paris St-Germain confirmed the shift conclusively: 11 goals, 15 assists in 34 games in all competitions - more assists than goals for the first time in his career at club level. "A goalscorer who became an Iniesta," as one Argentine analyst described it.

Messi's finest moment as Argentina captain came when he won the World Cup four years ago.

Running alongside the tactical evolution was a parallel story that took even longer to resolve: the question of who Messi was for Argentina. He became captain in August 2011. Then came the defeats. The 2014 World Cup final, lost to Germany in extra time in the Maracana. The 2015 Copa America final, lost on penalties to Chile. The 2016 Copa America final, lost on penalties to Chile again. Three finals in three years, all lost, and each one tightening the knot of public expectation around him. After the last one he quit, something he had considered twice before. He came back. But he was different.

At the 2019 Copa America, eliminated controversially by hosts Brazil in the semi-final, Messi walked into a press conference and strongly criticised the South American football confederation. This was not the player who had once seemed to retreat into silence when the weight of Argentina became too heavy. This was a leader who had decided to stop being defined by what he hadn't won.

The Copa America 2021 was the release. Argentina beat Brazil in the Maracana final and ended a 28-year wait for a major title. The pre-match team talk Messi gave moved the dressing room to tears. The Messi at the 2022 World Cup was something else again - a synthesis of everything that had come before. There was the sprint past Josko Gvardiol in the semi-final against Croatia, the 2009 winger reappearing for one extraordinary moment. There was the quarterback precision in the final against France - the pass to put Nahuel Molina through, the ghost-run to force the rebound for Argentina's third goal, the penalties converted when everything was on the line.

"Football changed a lot," Messi told Zinedine Zidane in a 2023 interview. "The way of playing, the systems. The game today is much more tactical and physical than before. Before, you found more spaces." He said this with the matter-of-fact tone of someone who has played across three distinct tactical eras of the modern game - the physical midfielders of Porto and Chelsea, the positional and passing peak, the post-Guardiola tactical arms race with quick transitions - and come out on top of all of them.

Lionel Messi joined Major League Soccer side Inter Miami in July 2023.

Messi walks more than he runs. Critics once used this against him. Now it reads as mastery. He is reading the game, conserving energy for the moments that matter. "The last Messi is always the best Messi," Pablo Aimar - his childhood idol - once said. He is probably still right.

What Messi has achieved across two decades is not just an accumulation of trophies and statistics. It is a re-imagination of what a footballer can be at every stage of a career. The teenage winger who dazzled Capello. The false nine who redrew the tactical map of European football. The enganche who learned to make others great. The captain who finally became what his country needed him to be - the quarterback of a World Cup-winning team. And now the veteran who barely runs and still sees everything first.

The World Cup build-up will generate many superlatives about Messi. Most of them will miss the point. The point is not how good he is but, how many times he has had to become someone completely new.