Here's why Messi, Mbappe and other soccer stars aren't playing in the Olympics

But many of the teams' best players, Argentina's Lionel Messi and France's Kylian Mbappe, will not make it onto the pitch. 

The reason for the absence of some of the world's biggest soccer stars all comes down to Olympic men's soccer roster rules. 

Why isn't Messi playing in the Olympics?

The soccer tournament at the Summer Games allows for 18 players on each team, but those positions are heavily restricted for those under 23 years of age. 

Each team is allowed three exceptions for older players.

That quickly led to speculation Messi could be included in Argentina’s squad, though Inter Miami would likely not have been too happy about its just-turned 37-year-old icon playing at the Olympics in the middle of the MLS season.

The Summer Games also come at the heels of the Copa America tournament, where Messi helped defend Argentina's title in a final against Colombia - while injuring his ankle. 

Even before the injury, the World Cup champion admitted he needed time to rest and wasn't going to play in the Olympics. 

"I have to choose carefully, and it would be too much to play two straight tournaments," the Argentinian player told ESPN ahead of the Olympics.

Some of soccer's future stars may get to play on the world stage because of the under-23 rule.

After all, Messi was previously featured in the 2008 squad at just 21-years-old, beating Nigeria 1-0 in a gold medal match.

Is Mbappé playing in the Olympics?

Unlike other major international soccer tournaments like the World Cup, European Championship and Copa America, the Olympic men’s soccer event is not featured on world governing body FIFA’s International Match Calendar, meaning clubs are not required to release players to compete at the Games.

“I have always had the same ambition,” the World Cup champion said in March. “I have always said that I wanted to go, but it doesn’t depend on me.”

So despite Mbappé's desire to be part of France’s team — the decision was not his to make as he’s joined Real Madrid. And even Macron’s plea for Madrid to “free up Kylian for the Olympic Games,” didn’t work.

The Associated Press contributed to this report.