Argentina head into the World Cup carrying a different kind of pressure. As defending champions, they will be one of the teams every opponent wants to beat, but the title also brings confidence and belief that few sides can match. History, however, is not on their side. No nation has successfully defended the World Cup since Brazil achieved the feat in 1958 and 1962. In recent tournaments, defending champions have often struggled, with Spain crashing out in the group stage in 2014 and Germany suffering the same fate in 2018. France bucked the trend by reaching the final in 2022, but retaining the trophy remains one of football's toughest challenges.Argentina's World Cup defence rests on one man again: Lionel Messi (AFP)Despite those historical hurdles, Argentina possess a trump card in Lionel Messi. Though he is in the closing stages of a remarkable career, his influence remains immense. Few players can change the course of a match as effortlessly as Messi, whose moments of brilliance continue to define the biggest occasions. As Argentina begin another World Cup campaign, they will once again look to their captain to provide the inspiration and magic that carried them to glory four years ago.Argentina arrived at the 2022 World Cup with a squad operating at its peak and a Lionel Messi determined to complete the one achievement missing from his glittering career. The captain delivered one of the finest individual campaigns in World Cup history, winning the Golden Ball for a second time and leading Argentina to their first title since 1986. Four years on, the challenge is far more complicated. While Messi remains the team's biggest match-winner, several key players from the triumph in Qatar are no longer at the same level. Argentina's defence, once a major strength, enters the tournament with question marks. Gonzalo Montiel, Nahuel Molina, Lisandro Martinez and Nicolas Tagliafico have all struggled to maintain the standards they set during the title-winning run. Cristian Romero remains a crucial figure but arrives after an injury setback, while veteran Nicolas Otamendi is nearing the end of his career. As a result, greater responsibility may once again fall on goalkeeper Emiliano Martinez, whose heroics played a decisive role in Qatar and could prove just as important if Argentina are to mount another serious challenge.The midfield has undergone significant changes since Argentina's triumph in Qatar. Rodrigo De Paul and Leandro Paredes are no longer competing in European football, while the retirement of Angel Di Maria has removed one of the side's most experienced and influential figures. As a result, much of the creative and physical burden will fall on Enzo Fernandez and Alexis Mac Allister, who have become central to Argentina's plans. Their ability to control possession, dictate tempo and link defence with attack will be crucial if the team is to make another deep run in the tournament. Messi, too, is likely to operate in a deeper role at times, using his vision and passing range to create opportunities for the forwards.Up front, however, Argentina remain blessed with match-winners. Messi, Lautaro Martinez and Julian Alvarez form one of the most dangerous attacking trios in international football, with each capable of deciding a game on his own. Lautaro endured a disappointing 2022 World Cup but arrives this time in outstanding form and eager to make a bigger impact on the grandest stage. Alvarez, meanwhile, has built a reputation for delivering in high-pressure matches, and few stages are bigger than the World Cup to further enhance that standing.Lionel Scaloni knows how to do itFew coaches understand their team as well as Lionel Scaloni understands Argentina. Since taking charge, he has guided the country to two Copa America titles and a World Cup, building one of the most united squads in international football. Questioning his ability to get the best out of this group would be difficult, given the success he has delivered. Alongside Lionel Messi, Scaloni has shaped the identity of the team and created an environment where the players are willing to fight for one another. That spirit was on full display during the heated quarter-final against the Netherlands at the 2022 World Cup, when emotions boiled over and the entire squad stood together. Argentina's unity remains one of their greatest strengths heading into another World Cup campaign.