This video will prepare you for the U.S. national team's next World Cup game, which is against Belgium. You'll sound like an expert to your friends and co-workers. (Tom LeGro/The Washington Post)

DaMarcus Beasley speaks from experience, of which he has plenty. So no one has to explain to him what’s on the line when the U.S. national team steps on the field Tuesday.

“This is what players live for,” Beasley said. “You live to play these types of games.”

By now, Beasley has played many of them, and he knows if the United States can’t get past Belgium in the World Cup’s knockout round, fans could be watching the curtain close on one of the most decorated international careers any U.S. player has assembled.

This is the fourth World Cup in which Beasley has appeared in a game. Fewer than 30 players — and no other Americans — have played in that many, a list that includes legends Pele and Diego Maradona.

“Without a doubt,” midfielder Michael Bradley said, Beasley is “one of the best players in U.S. soccer history.”

U.S. and Belgian World Cup comparison

“What he has done for club teams he has been on, what he has done for the national team, the consistency, the longevity,” Bradley said, “and he continues to show how important he is for us.”

Beasley’s most impressive accomplishment isn’t that he has survived this long; rather, it’s how he’s done it. He’s not the same player who slipped on a U.S. jersey 13 years ago. That guy flew up and down the side of the pitch, his legs moving faster than a hummingbird’s wings.

“When he was younger, he was probably loud and brash, but he’s calmed down,” U.S. goalkeeper Tim Howard said of Beasley. “He’s quiet, he’s a dad — just all the things you’d hope from someone as they mature.”

The energy is still there, enough to allow him to shuttle back and forth between the team’s veterans and its young players. Tuesday will mark his 11th appearance in a World Cup game, one behind Landon Donovan for most among Americans, and his 120th with the U.S. national team, fifth all-time. But unlike that Beasley who was fluttering his way through the 2002 World Cup, this 32-year-old version is able to appreciate the moment. He knows it could be his last chance to help his team return to the tournament’s quarterfinal round.

“It seems like he gets younger and younger. He never gets tired,” U.S. Coach Jurgen Klinsmann said. “You want to go home at 3 o’clock at night. ‘Say, DaMarcus, do you want to kick the ball around?’ He’s right there.”

The biggest transformation has taken place on the field. A 20-year-old Beasley was offense-minded and goal-oriented. But the Beasley in this tournament, while still a capable attacker, is a fullback tasked with significant defensive responsibilities.

“Back in those days I always wanted to score goals and make the last assist or something like that. But now it’s a different mind-set and I’ve taken on a new position, a new position I like,” said Beasley, who has played for Mexico’s Puebla since 2011 after several seasons bouncing among European teams.

He still gets up and down the field and seems always to be around the ball, but Beasley hasn’t scored a goal in international competition since 2008. Still, he’s as important as anyone on the field, especially with a back four that has faced plenty of scrutiny heading into the tournament.

“I think that’s the thing with Beas that always excited me,” Howard said, “once he accepted playing fullback. I thought he’d be brilliant. I’m a big fan of wingers becoming fullbacks. I just think it’s a natural progression.”

At times, Beasley can be a sage in cleats, a veteran who’s helping just as much off the field. The U.S. defense still feels like a work in progress, as Klinsmann tweaked the starting lineup before the Germany game, replacing veteran Geoff Cameron with 25-year-old Omar Gonzalez. The younger players say Beasley has been generous with advice but also quick to give encouragement or congratulations. Other times he sets an example without ever opening his mouth.

“Nothing really freaks him out,” said Gonzalez. “He is always calm, cool, collected and it is great having a guy who’s that secure and knows what is going on in the back line.”

The U.S. team’s fate could hinge on it. Belgium won its three group stage games by one goal apiece and with the U.S. offense struggling to find the net, Tuesday’s match could be a low-scoring affair. As it has for the past dozen-plus years, the American squad will look again to Beasley, who has changed himself and his game to evolve into the player his team needs most.

“I still play the same,” Beasley said. “I still play with the same heart and desire to win every game, to win every tackle, to maybe score a goal — doesn’t matter.

“I like big games. I like being under the lights. I like playing in front of 80,000 people.”