Lionel Scaloni did not know where to look. In the dugout at Arrowhead, Argentina’s coach was caught in the emotion of it all. Lionel Messi was trudging towards him, his number up, ready to be replaced.As he did so, Scaloni made an unconvincing attempt to keep calm with his team 3-0 up against Algeria.It was a moment reminiscent of Qatar four years ago when Scaloni’s then-assistant, Pablo Aimar, the player Messi idolised as a boy, put his head in his hands and slumped in his seat. Aimar cried uncontrollably after Messi scored a goal against Mexico that liberated 46million Argentinians from an almost unbearable tension.In Kansas City, Scaloni tried to hold it together. He pulled Messi in, shouted words of gratitude in his ear, and blinked over and over again, apparently welling up.Lionel Scaloni’s admiration for Lionel Messi is written all over his face (Tom Weller/picture alliance via Getty Images)“It’s quite hard to explain,” Scaloni said. “We’re still amazed by him even though we get to see him on a daily basis, and he’s been the best for 20 years. He still pulls it off in every single match, and you don’t have to be an Argentina fan to admire what he’s done at age 38.”Get free access to the most comprehensive World Cup coverage in The Athletic app.Up in the commentary box, Messi’s former team-mates, Carlos Tevez and Sergio Aguero, began bowing down. Messi was performing new tricks even on his 200th appearance for his country. He started Argentina’s title defence with his first hat-trick at the World Cup and drew level with Miroslav Klose as the tournament’s all-time leading scorer. Astonishingly, El Diez (the 10) looked as good as ever. “I’m feeling really good,” Messi laughed, taking it as a compliment.His rivals were also in a state of utter disbelief. Earlier in the day, Kylian Mbappe scored an impressive brace against Senegal. But as was the case after the 2022 World Cup final, it was Messi who stole the headlines.Boarding a flight back to Norway's training base in Greensboro, North Carolina, having scored a couple of times himself against Iraq, Erling Haaland posted an incredulous selfie on Instagram. "Messi is a madman."His former team-mate Xavi told The Athletic: "When you look at Leo, he hasn't changed. Physically, he's still the same, still fit. Look at the way his feet still move, that fast little shuffle: tsk, tsk, tsk. How is that possible?"Algeria players were mesmerised by Lionel Messi's movement (Du Yu/Xinhua via Getty Images)Even Scaloni struggles for an answer. After the Algeria game, he spoke about Messi's naturalidad, the way things still come so easily to him. "I could stay here with you for over an hour trying to explain what he does," Scaloni said. "But you need to be there to really understand the atmosphere, the ambience. It's really hard to put into words."So how on earth does he do it — and keep doing it?Messi playing in a sixth men's World Cup, a record he shares with Cristiano Ronaldo, was simultaneously expected and in doubt. He didn’t publicly commit to it. He kept the public guessing. In March, the final international break before the tournament, Scaloni claimed to still be in the dark about Messi's intentions."I'll do everything I can to make sure he's there," he said. "For the sake of football, he has to be there. It's not me who decides. It's up to him, his state of mind, his physical condition."It's difficult because it is not just the Argentinians who want to see him, everyone wants to see him. I want him to be there. It's up to him to decide. He's earned the right to make that decision with peace of mind. We're in no rush about it. We know whatever he decides will be best for the team and for him. We hope he will be there."Sources familiar with Messi's plans, speaking on condition of anonymity, have told The Athletic he did not take this World Cup for granted. Before the final in 2022, he told reporters: "I am proud to be able to finish my World Cup journey playing this final. What I'm experiencing is exciting. Sunday will be my last game in a World Cup."When the emir of Qatar placed a bisht on Messi before the trophy lift in Lusail, many, including Messi, thought that was it. The World Cup in the United States, Canada and Mexico felt a long, long way away.It may sound strange given he is considered the greatest player of all time, but, as this summer’s World Cup drew closer, Messi felt the need to prove to himself that he could still make the difference for Argentina.Those around him were incredulous. In their opinion, Messi would not only still be good enough. He'd be the best player for Argentina and the best player at the World Cup. "Anyone else would have retired after winning it in 2022," Xavi tells The Athletic. "But he's such a competitive animal."What mattered to Messi, however, was to be called up on merit, not reputation — present prospects rather than past glory. When Messi moved to Inter Miami in July 2023, it felt, on one level, like he was preparing and maturing the American market for the upcoming World Cup. Playing in MLS would, theoretically, allow Messi to adapt to the unique conditions in the States. Conversely, some thought it might wear him down too.