On Wednesday, the best in MLS will face off against a team of All Stars from Mexico's top flight for the second time in a battle between the top two leagues in North America. The MLS All-Stars won the inaugural edition last year in a penalty shootout after regulation time ended in a 1-1 draw.
Zimmerman said there was a different feel to last year's game than to previous years in which the MLS All-Stars played against a top team from Europe or in an intra-league East versus West format.
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"We played Atletico Madrid in Orlando in 2019, and it was competitive -- you're wanting to prove that you can play at a high level," Zimmerman said ahead of the game in Saint Paul, Minnesota (watch live on ESPN at 8:30 p.m. ET). "But the competitiveness on the field last year in L.A. against Liga MX was definitely a new step in terms of the competition."
Later year's game marked the debut of a new format in an event that has evolved since the league launched in 1996. The game originally pitted Eastern and Western Conference squads. An all-American squad played a squad of international MLS players in 1998. From 2005 to 2019, the MLS All-Stars played an invited club team from one of Europe's top leagues.
But the current format reflects the direction both leagues are moving. Beginning in 2023, MLS and Liga MX will reintroduce a joint competition called the Leagues Cup, this time with all 47 of the leagues' clubs competing and both domestic leagues taking a break for the event.
The shift in format -- and the convergence of the two leagues in playing regular competitive matches -- coincides with continued success for MLS against its rival league to the south. Seattle Sounders FC won the most recent CONCACAF Champions League this year and MLS teams have won all four of the Campeones Cup matches played against Liga MX since 2018.
"I think being from Europe, and coming here 13 years ago, I've been on the outside and watched it, I think this is the closest that MLS has ever been to Liga MX," said U.S. All-Star coach Adrian Heath. "I think 13 years ago when I arrived, the gap was pretty big but it's been continually closed, and closed with the investment that the clubs have put into their clubs in the U.S."
LA Galaxy striker Javier "Chicharito" Hernandez is one of several MLS All-Stars with Liga MX experience, having started at Chivas before moving on to a career in Europe at Manchester United and Real Madrid, among others.
"The narrative always is about asking which [league] is better and how they are doing. They get compared between each other a lot," Hernandez said. "It doesn't matter which league is doing better, Liga MX will have to learn and utilize lot of things that MLS is doing well.
"Also the MLS is seeing all the qualities of Liga MX and some of them have been added. They must learn from each other. But yeah, we're going to go Wednesday and try to win."
The game also provides a chance to see some players who could play at the World Cup in Qatar later this year. On the Liga MX side, Cruz Azul's Uriel Antuna and Chivas' Alexis Vega are both likely to be included on Mexico's roster.
And there's some crossover, too. The Galaxy's Julian Araujo is an MLS All-Star who could play for Mexico in Qatar.
But just because there's ever-growing connections between the two leagues, the MLS All-Star Game isn't necessarily going to be an exhibition.
"It's a competitive atmosphere," Zimmerman said. "The game is not something that you see in a typical All-Star game, whether that's the NBA or baseball, this is very competitive."
Information from Reuters and the Associated Press was used in this story.