IF YOU WERE A 20-YEAR-OLD soccer phenom in the summer of 2002, poised to turn the American game on its head, a good place to show up would have been the World Cup finals in Japan and South Korea. As a billion or so fans watched worldwide, dark-horse team after dark-horse team took kamikaze runs at the sport's big battleships. France's hopes were sunk by Senegal. South Korea knocked out both Italy and Spain. And a formerly unimportant soccer concern known as "the Americans"—who'd placed 32nd out of 32 countries in World Cup '98—scored three goals in 36 minutes to defeat fifth-ranked powerhouse Portugal. The U.S. made it to the quarterfinals—their best showing since 1930—thanks in large part to that 20-year-old: a forward from Redlands, California, named Landon Donovan, who scored more than a quarter of the team's goals in his World Cup debut.

Four years later, Donovan is one of the highest-paid soccer players in America, owing to his reported $4.8 million contract with the L.A. Galaxy. But Major League Soccer is still far from mainstream: The league is composed of just a dozen teams, with a smaller fan base than figure skating. And even as the MLS's unofficial ambassador,

"To make the plays," says donovan, "you need equilibrium between the cardiovascular, the muscular, and the mental."

Donovan is by no means a household name—yet. Only outside the country is the quick forward widely recognized as the megathreat he is: America's greatest hope for victory in the 2006 World Cup, which kicks off June 9 in Munich.

If soccer players reflect their national character—the flamboyant Brazilians, the Germans with their iron discipline—then Donovan is a poster boy for both hard-boiled American ingenuity and our insatiable desire for self-improvement. Sure, he's got style, with his silky gait and fondness for soaring horizontally through the air, but what sets Donovan apart isn't flair or technical prowess; it's speed and fitness. He's spent the past four years developing an endurance-training strategy that capitalizes on his natural assets and—as a nice perk—ramps up his ball-handling skills.

Donovan designed his regimen around the situation he fears most: getting the ball but not having sufficient energy reserves to score. In a 90-minute soccer match, players can manage a strong running game for the first hour, but sometime between the 61st and 75th minute, their metabolic machinery tends to discombobulate, and they simply run out of breath.

This is where Donovan's Kenya theory comes in.

"The Kenyan runners who always win marathons never jog," says Donovan. "Ever." At five foot eight, he's small-boned and compact, with the intelligent smirk of a seasoned pro. "They always run at 90 percent of capacity, teaching their heart and body to endure." So Donovan never jogs. Instead, he trains at 80 percent of his maximum heart rate until he's exhausted, running through obstacle drills, lifting weights, and teaching his body "recovery endurance" through a sequence of sprints and rests. Then he chases all that with a team scrimmage that lasts up to 90 minutes.

This ability to push yourself to the brink of collapse and then recover quickly is essential for aerobic endurance, but Donovan has seen even greater benefits: Now that he no longer worries about his wind petering out, he can focus on the field, and his technical skills have improved as a result. "Soccer's a mental game," he explains. "To keep your concentration, to make the plays, you need equilibrium between the cardiovascular, the muscular, and the mental."

Natural talent comes in handy, too. Raised in Southern California about an hour east of L.A., Donovan was five when he scored seven goals in his first youth-league game. In 1999, at 17, he graduated from high school and went to play for Germany's Bayer Leverkusen pro team. At the time, the MLS was just three years old and notorious for being the globe's worst league; the only way to earn a living playing soccer was to cross the Atlantic. After spending a miserable year warming the bench, Donovan came home to join the MLS's San Jose Earthquakes in 2001. In 2005, he joined the Galaxy.

Back on home turf, he discovered that peak form isn't just about scoring goals; it's about experimenting with fitness strategies and making your own rules. "When I finally did yoga for the first time this year," Donovan says, "there were chubby guys in the room kicking my ass. Yoga is intense; it's muscular. But there is nothing better than flexibility." He's also become a food autodidact. Raised in the era of carbo-loading and pasta parties, Donovan has renounced monomaniacal food-group consumption for a more well-rounded menu of fresh fish, fruit, and broccoli. "I found out Michael Jordan ate a 20-ounce steak before each game," he says. "This year I started balancing carbs with protein before a game and I've had unbelievable energy every time I step on the field."

The star is finding balance off the field, too. After six years away from home, Donovan has settled back into a familiar SoCal routine, living in a Manhattan Beach bungalow with his fiancée, 29-year-old actress Bianca Kajlich, and their three dogs and cat. He dreams of soccer—and putting the dark-horse Americans on the map. "In countries like Brazil, the best athletes are playing soccer," he says. "Meanwhile, in America, the best athletes are playing football, basketball, and baseball. Soccer isn't close to its potential yet, and that's where growing the game comes in.

"I keep in mind that famous Joe DiMaggio quote," he adds. " 'Always swing for the fences at practice in case the kids are out there.' "