This is Lionel Messi’s world and we are all still living in it.At the age of 38, playing in his sixth World Cup, he scored a hat-trick in Argentina’s 3-0 win over Algeria in Kansas City to take him level with Germany’s Miroslav Klose as the all-time top scorer at a men’s World Cup.After such an emphatic opening display from the holders, few would bet against Messi adding to his 16 World Cup goals as the tournament progresses.Jack Lang and Oliver Kay dissect the key talking points…Lionel Messi strikes againLionel Messi is probably the last player you could ever describe as an unknown quantity. Still, in the weeks leading up to his sixth World Cup, a few doubts hung in the air. How fit would he be? Would he be a guaranteed starter for Argentina? Would he still, with his 39th birthday just around the corner, have the energy and drive to dominate matches at this level?It only took him 45 minutes to make all of those questions look deeply idiotic.With four minutes on the clock, Messi was back in his own defensive third, winning the ball back. A little later, he was haring after Algeria defenders. Age? Only a number, amigo. This was as lean and mean as Messi had looked for some time, the walking of recent years replaced with something far more urgent.On the ball, he was as decisive as ever. He whipped a finish past Algeria goalkeeper Luca Zidane, only to be denied by a late offside flag. He swapped delicate passes with Thiago Almada and Rodrigo De Paul, yanking the Algerian defence out of shape. Then there was the opening goal.Sure, Luca Zidane should have done better with the finish. But go back to the start of the move and you will see Messi, back on halfway plotting a route through, the architect and the assassin in the same move.Lionel Messi scores Argentina's opener (Tom Weller/picture alliance via Getty Images)There was more to come in the second half. Messi played a gorgeous pass that led to a Lautaro Martinez chance and, on the hour mark, plundered his second of the night after a goalkeeping error.Then came the final flourish, a trademark finish whipped into the bottom corner from the edge of the box.Conclusion? Ditch the doubts. We're still living in Messi's world.Jack Lang...but should he have been sent off?As brilliant and utterly irrepressible as he is, there have been a few occasions during his illustrious career when opponents — and certainly opposition fans — have suggested that Messi has received “special treatment” from referees.What is certain is that, between scoring his first and second goals against Argentina, he got lucky. A challenge on Algeria captain Aissa Mandi, who was caught by Messi on his right calf and Achilles tendon, could have earned at least a yellow card — and plausibly a red card — but Polish referee Szymon Marciniak was content to award a free kick.Lionel Messi's challenge on Aissa Mandi went unpunished (Tom Weller/picture alliance via Getty Images)It was a strange incident. Mandi was in control of the ball, going nowhere fast, and there was little prospect of dispossessing him from Messi’s position. To make a lunge like that, with his studs up, seemed incomprehensible, never mind dangerous.Special treatment? At the very least it was lenient refereeing. A yellow card would perhaps have been the most widely expected outcome — a red card second — but Messi was certainly lucky to get away scot-free.Oliver KayWho is Luca Zidane?Never easy, following in the footsteps of your father. Especially when your old man happens to be one of the best footballers of all time.Luca Zidane, in fairness, has broadly made a decent fist of it. He was good enough to play for Real Madrid and has carved out a solid career for himself across some of Spain's less prominent clubs. It probably helped that he decided to be a goalkeeper; any comparisons with his dad, France legend Zinedine, begin and end with physical similarities.Luca Zidane was watched in Kansas City by his father, France legend Zinedine Zidane (Juan Mabromata/AFP via Getty Images)Zidane Jr played for France at youth level. Only last year did he make the switch to Algeria. His performances in the Africa Cup of Nations helped convince fans that it was no PR stunt on the part of coach Vladimir Petkovic.Here, though, on his World Cup debut, wearing a mask after suffering a broken jaw in the spring, he had a night to forget. Messi's first swerved a little in the air but he should still have got a stronger hand to it. And the second was a howler, pure and simple. The third? He had little chance.Let's hope the great Zizou has some words of comfort for him in the days ahead.Jack LangHow good did Argentina look?This is the third time Argentina have gone into the World Cup as defending champions — and the first time that, as holders, they have avoided defeat in their opening game.Traumatic defeats for Argentina at the hands of Belgium in 1982 and Cameroon in 1990 are part of a wider trend that has also included famous defeats for France (against Senegal in 2002), Spain (against the Netherlands in 2014) and Germany (against Mexico) in 2018. In four of the previous six tournaments this century, the holders were knocked out in the group stage.Passionate fans in Kansas City were treated to an impressive display from Argentina (Maja Hitij/FIFA via Getty Images)With a comfortable victory over Algeria, though, Argentina have already taken a significant step towards the knockout stage, with games against Austria and Jordan. In a tournament when some of the favourites, notably Brazil and Spain, have started unconvincingly, Argentina coach Lionel Scaloni will be more than happy with his team’s opening performance.If there are questions of an over-reliance on Messi, they will not trouble him any more than they did in Qatar in 2022.Oliver KayWhen do they play next?Group J, Monday June 22:Argentina vs Austria: 1pm ET (6pm BST), DallasAlgeria vs Jordan: 11pm ET (4am BST, June 23), San FranciscoIf Argentina or Algeria win the group, they’ll play the Group H runner-up in their first knockout game in Miami on July 3.If they finish second, they’ll play the Group H winner in Los Angeles on July 2.If they advance as a third-place team, they’ll play a group winner from Group B, D, G, K or L in Atlanta, Kansas City, San Francisco, Seattle or Vancouver.