Lionel Messi and Patrick Mahomes swapped autographed Argentina national football team and Kansas City Chiefs jerseys in a moment captured on social media by Major League Soccer.

The monthlong soccer tournament is the brainchild of FIFA President Gianni Infantino. But slow ticket sales and complaints from overworked players suggest its success is hardly an open goal.

Running through July 13 in 12 U.S. cities, the tournament doubles as a high-stakes dress rehearsal for the 2026 FIFA World Cup.

In Barcelona, Messi elevated club football to a previously unimaginable realm. Between 2009 and 2015, he formed the most telepathic midfield-forward connection in football history with Xavi and Andrés Iniesta. He scored 91 goals in a single calendar year and broke virtually every meaningful club record.

With the first Club World Cup match on June 15, it's time to get up to speed with the key talking points around the tournament