When Lionel Messi swept home a trademark left-footed curler in Argentina's second World Cup match against Austria, he was not just getting his team off to a strong start.

The 38-year-old was also making history, becoming the World Cup's all-time leading goalscorer, and demonstrating that he still lays claim to being the king of world football.

Messi is enjoying a scintillating start to the tournament as Argentina defend their title.

With a hat-trick in the opening game, the record broken in the second, and a third game against Jordan to come, he is a strong contender for the Golden Boot, awarded to the top goalscorer at the finals - one individual prize he has never won.

Messi has now scored in six consecutive World Cup matches, a feat only achieved by two other players - France's Just Fontaine and Brazil's Jairzinho in 1958.

No player has ever scored in seven straight matches.

The Inter Miami forward has also created the most chances in World Cup history - he is one assist away from providing more than any other player since records began in 1966, according to Opta.

He currently shares that record with his idol, Maradona.

A new generation of superstars like Kylian Mbappe, Erling Haaland and Vinicius Jr may already be making their own marks on the tournament, but if they want to claim the crown, they are going to have to outperform Messi.

So how exactly can Messi - who turns 39 on Wednesday and has been playing in Major League Soccer (MLS) for three years - still be delivering rampant, raucous performances on the biggest stage of all?

When Messi - then aged 31 - and Argentina were knocked out by France in a seven-goal classic in Russia in 2018, the days of him delivering tournament-defining performances in the World Cup could have been over.

But four years later he captained his country to the trophy in Qatar, scoring seven goals, and after a further four he has become the first ever player to score in six consecutive World Cup matches.

Olivier Giroud was part of the France side which went on to win that 2018 edition, and still playing in Ligue 1 himself at 39, can relate to Messi's situation and believes a player's competition with himself is more important than thinking about the younger generation.

"It's clear just how passionate Messi still is for football and you can tell it's in his DNA to always be a competitor, and to try and outdo himself more than anyone else," Giroud says.

"Playing at a high level at our age, you have to pay close attention to your life hygiene - how you sleep, your diet, and taking care of your body, because that's the thing you rely on for work.

"The key thing is still having the desire, the motivation, the passion, to keep going."

Messi is not the only global sports superstar to have continued laying down gauntlets for younger rivals into their late 30s - tennis' Novak Djokovic being perhaps the most impressive example in recent years.

But doing so requires a combination of relentless dedication to physical fitness and unerring self-belief.

"Players know themselves inside out by that age, so there's not a lot left to teach them about how to manage as they get older," says Michael Caulfield, a sports psychologist working in professional football for more than 20 years.

"From a physical point of view, they take advantage of every breakthrough in sports science.

"But mentally, it's about whether they have the capacity in their minds to deal with the daily grind. They have to be willing to spend the whole year working hard on the same things, and if you've been doing that for 25 years, that takes huge self-discipline.

"They have to maintain the sheer will to go through the rehab process after injuries when they know they've already won everything.

"All the top athletes I've ever known, they're all willing to try and go back one more time, because they love doing what they do.

"It's the same reason you still see Bruce Springsteen or Madonna touring - it is completely intrinsic to who these stars are."

Generally considered a reserved and humble character, Messi has occasionally demonstrated a will to revel in his personal stardom, including when he hoisted aloft his own shirt in front of Real Madrid fans after scoring an injury-time winner in an El Clasico victory in 2017.

"When he crosses the white line, he is a very different person," says his former Barcelona team-mate Cesc Fabregas in the BBC iPlayer documentary Rivals: Messi vs Ronaldo. "He wants to win at any cost."

That relentless desire to succeed can underpin a sports career long after a star like Messi has achieved everything their discipline has to offer, as can the sheer love of the game of itself.

"Athletes always think there's something left to achieve," says Caulfield. "They're wondering if there is something they haven't quite mastered yet.

"But more than anything they want to keep feeling that childlike joy of doing what they love. You see Messi still doing keepy-ups or a rondo, and he still loves football like a little boy."

Messi's incredible display drew stark contrast with his perennial rival, Cristiano Ronaldo, who is playing in his sixth World Cup with Portugal.

The 41-year-old made very little impact in his side's opening draw with DR Congo, and those who know him best believe Messi's display will have played on his mind.

"Ronaldo will have been fuming," Rooney says. "Even at 41 he will still be expecting to be top goalscorer. But that attitude is part of his own greatness. The two of them have spurred each other on.

"They have this self-belief and arrogance, in a good way, where they know they what they have done, have nothing to prove, and it's up to the likes of Mbappe and Haaland to prove they can take over."