Juan Mata's list of recent travels reads like the highlights of a glamorous, expensively planned, but hastily executed vacation.

Based on a look through the Chelsea and Spain midfielder's verified Twitter feed, Mata has visited the NBA Finals in Miami, New York's Central Park and a Brazilian beach in Recife. He has trained in Madrid and played in Yankee Stadium. He has photographs outside the U.K. Houses of Parliament and the Gateway Arch in St. Louis to go with at least 10,000 miles' worth of air travel.

Spain's Juan Mata reacts after scoring a goal against Italy during their Euro 2012 final soccer match at the Olympic stadium in Kiev last July. Reuters

All that was just in the four weeks since the Premier League season ended. In every city there was a game to play or a training session to work through

Then again, the concept of seasons ending is more a convenience of the calendar than a reality to Mata. For the past five years he has been one of the busiest men in world sports and a constant
reminder of the demands made of elite players.

Indeed, his 2012-2013 campaign formally began 10 months ago at Wembley Stadium in the Community Shield, though there were also preseason exhibitions. And, as of Sunday night, it still wasn't over when he took the field in Brazil for Spain's Confederations Cup opener against Uruguay.

Should Spain progress in the tournament, Mata could be playing in the final on June 30. Seventeen days later, Chelsea is due in Bangkok for an exhibition match and the whole thing will start again. For Mata, this is the reality of being 25 years old and playing for two sides that have the most packed schedules in the world.

This past season, Chelsea club played 69 games, the most by any team in the top four European leagues, according to Opta Sports.

Of those, 38 came in the Premier League. The rest were down in large part to Chelsea's progress in the domestic-cup competitions and one of the longest possible European campaigns. The club first played six matches in the Champions League group stage, where it finished third, before
being dumped into the Europa League Round of 32 and progressing to the final. That's a total of 15 European games—even Bayern Munich, winner of the Champions League—didn't play that many.

"The problem we had this year was too many games," former Chelsea manager Rafa Benitez said in May, assessing the effect the schedule had on evaluating his own players. "Two games a week for the whole season [makes it] difficult to see the real level. If you played less competition, I think you can manage better and with fresh legs win even more games."

But this isn't new to Mata, who might take some convincing that most players actually get a break—however short—almost
every summer.

He grew up on the younger side of Spain's golden generation, just as it came to dominate virtually every level of the international game. And so, every summer seemed to bring another call-up to a national team for Mata. In 2006, he was in the Spain squad that won the Under-19 European Championship. The next year he was at the Under-20 World Cup.

In 2008, he missed out on the senior squad's triumph at the Euro, and that might have been his last summer without a major tournament. By 2009, he was firmly in the senior team's fold, so he went to the Confederations Cup, the 2010 World Cup, and Euro 2012. Conveniently, he was also still young enough to go to the Under-21 Euro with Spain in 2011 and last year's Olympic tournament, too.

That breathless list leaves him with some 284 appearances for club and country since the beginning of the 2008 season, including at least 220 starts. It also seems incredible that in that span, playing in the physically punishing English Premier League, Mata hasn't suffered an injury serious enough for him to miss significant playing time.

You don't have to look far to find other players in the same boat. Pretty much anyone who has been a regular for Barcelona over the past five years knows the feeling. Not counting preseason exhibition matches, it has played 307 games in all competitions over the past five years. That's only nine short of the maximum 316 that would have been possible for Barcelona if it had reached the final of every tournament it entered.

Take right back Dani Alves, who is also a stalwart of the Brazilian national team. He played all 90 minutes in Brazil's 3-0 victory over Japan in Saturday's Confederations Cup game, even providing an assist for Paulinho. Alves, 30, has made a Mata-esque 282 appareances in the past five years with 252 starts.

Technically, he is already working on his 2013-2014 tally, adding six starts for Brazil this summer.

All of this raises questions over the wisdom of making these players travel from their European bases to South America for the Confederations Cup, a tournament with only a fraction of the World Cup's prestige. The likes of Spain and Italy have nothing to prove there. Their World Cup qualifying matches this fall against teams like Bulgaria and Finland will mean more than anything they might accomplish over the next two weeks. Still, both teams took nearly full-strength squads to the tournament.

For Brazil, it's a different story. The Selecao, as the team is known, doesn't have to play qualifiers for the 2014 World Cup since it's hosting the tournament. So the Confederations Cup is a rare opportunity to play games in a competitive setting. Plus—and perhaps more importantly, it's a chance to redress the team's 22nd place in the FIFA World Rankings.

And, for that, Brazil has called up the players it deems necessary, exhausted or not.

Write to Joshua Robinson at joshua.robinson@wsj.com