am Querry of United States of America plays a backhand during his Gentlemen's Singles first round match against Bernard Tomic of Australia on day two of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 25, 20
Sam Querry of United States of America plays a backhand during his Gentlemen's Singles first round match against Bernard Tomic of Australia on day two of the Wimbledon Lawn Tennis Championships on June 25, 2013 in London, England.
Credit: Clive Brunskill / Getty Images
John Isner is weird, and not just because of his height; he's weird because in a sport that often deprives kids of their childhood, Isner has managed to lead a lusciously normal life. Unlike pretty much every other elite player, John Isner didn't turn pro in his teens or spend his youth at a tennis academy. Instead, he trained with local coaches in Greensboro, North Carolina, his hometown, and played college tennis at the University of Georgia. He stayed for all four years. When I talk with him later, he tells me with pride that he never missed a Bulldogs football game. His college experience, he'll say, was "very normal."

"He was the happiest child in the world," his mother, Karen, tells me over coffee the morning after his victory. "John's contemporaries all turned pro, the top junior players, at age 15, 16, 17. I can remember being at these big junior tournaments and everybody talking about who's going pro." Karen rests her chin on her hand. "And it didn't work out for any of 'em, really."

John's father, Bob, adds, "And I think part of the reason is the pro tennis game has changed . . . . You really need to be not a teenager. You need to be . . . ."

"Manly," Karen says.

The numbers show that the Isners are right. As tennis has become a more physical, grueling game that favors the tall and the strong, the age of the top players has crept upward. A decade ago, dozens of teenagers roamed the top 100; now there is one. The average age of a top 10 player is 26.

In some ways, then, Isner's a throwback to an era when more players went to college and joined the tour when they were older, but there's also something ultramodern about him that exemplifies the way the sport is evolving. You can point to John Isner and use him as evidence for all sorts of arguments, which is why it's fascinating to talk to executives about him; the language they use says a lot about how they see the world. To the USTA's Patrick McEnroe – a man who deals with standards, rules, consistency, scale – Isner is an outlier twice over. He's not just "a freak of nature because he's 6-foot-9 and has a monster serve," but because he didn't spend his youth at a tennis academy. But to Patrick's older brother, John McEnroe, one of tennis's great idiosyncratic geniuses, who played for one year at Stanford University, the quirks of John Isner are what make him worth talking about. "He went to college," John McEnroe tells me. "I think it's helped him. I'm sure it took him a while to feel comfortable with himself and his body, because he's so big. But he's made this progression. I was almost surprised it took this long."

John McEnroe is open about the fact that he and his younger brother Patrick don't see eye to eye on how to best train young players. "I would prefer the route that they mature later," John says, "and God forbid they play other sports and go to college. These crazy ideas I have." Since 2010, John has run his own tennis academy, the John McEnroe Tennis Academy, in New York, and it's not affiliated with the USTA, although he originally hoped it would be. When the USTA rebuffed his idea for a partnership, John set up shop at a private tennis facility called Sportime, located on Randall's Island, off Manhattan. It's organized so that, unlike the Florida tennis academies, kids can live with their parents, commute to the courts, play other sports, and basically live normal lives. "Some people believe, my brother being one, you gotta go to [the] Chris Evert [Academy], and USTA, and train and live and breathe it, otherwise you have no chance against this foreign invasion of players," John McEnroe says. He gives "foreign invasion" a skeptical inflection. "I would have quit the game if I would have been sent down there" – to Florida. "So I certainly want to provide the alternative for the kids who don't want to do that."

It's hard to say which McEnroe has the right idea, because their approaches boil down to different ideas about how to cultivate tennis genius, and no one knows where genius comes from. The two most dominant men's players of the last decade are also two of the flukiest stories. Rafael Nadal was a right-handed kid who grew up on a Spanish island, playing soccer, until his uncle Toni convinced him to start playing tennis as a lefty. Roger Federer was the son of parents who worked in the pharmaceutical industry.

To get some perspective, I decide to call L. Jon Wertheim of Sports Illustrated. He's the dean of tennis writers. His book, Strokes of Genius, is the definitive account of probably the greatest match of all time, the 2008 Wimbledon final between Nadal and Federer. I figure that if there's anyone who can tell me which way the wind is blowing for American tennis, it's Wertheim. Instead, he tells me there's no such thing as a weather vane. "People are using outdated metrics and expectations," Wertheim says. "It's a global sport . . . . I mean, do I think the USTA is great at finding and developing talent? No. But relative to how many people play tennis globally, the USTA is doing all right."

Wertheim asks me if I've ever heard of a woman named Alexa Glatch. Glatch, it turns out, was once a top U.S. prospect; in 2005, at the age of 16, she won a first-round match at the U.S. Open. Later, a dog darted in front of her motor scooter, and Glatch crashed, breaking her left elbow and her right wrist. "Suddenly her career's done," Wertheim says, "and it's like, U.S. tennis sucks." The point is that in tennis, sample sizes are small – there simply aren't a lot of elite players in the world – so one or two freak events can have a huge effect on a nation's perceived ability. And there is no better example of this fact than what happens in Switzerland and immediately afterward.

On the second day of Davis Cup competition, Mardy Fish and Mike Bryan defeat Federer and Wawrinka in doubles. It's the clinching match. The Americans were supposed to get shut out. Instead they sweep the Swiss 3–0. Suddenly everything looks different. It's so obvious now: the fragility of the Swiss, who relied too much on their superstar, Federer; the depth and grit of the Americans. I ask Courier what the victory means for American tennis more broadly, and he frowns and says, "I'd be careful ascribing too much meaning to an isolated circumstance like this."

After Switzerland, John Isner reaches the quarterfinals and semifinals of his next two tournaments, boosting his ranking from 17 to 11. Then in March he breaks through to the top 10 in the most impressive and dramatic way possible: by beating the No. 1 player in the world, Novak Djokovic. There's more: In April, Isner flies to Roquebrune, France, with the U.S. Davis Cup team for America's quarterfinal battle against France, and proceeds to drill the two best men France has to offer, Jo-Wilfried Tsonga and Gilles Simon, the No. 6 and No. 13 players in the world.

This summer, Isner might keep his streak alive, or he might revert to the player he used to be. Meanwhile, across America, hundreds of thousands of kids will learn to hit topspin with brightly colored foam balls, and a subset will learn to slide on clay. The cognoscenti will continue to debate the best way to train young players. Courier and his team will prepare for their Davis Cup semifinal against Spain in September. Sportswriters will discuss, prematurely, the ramifications of the "Isner Era." Younger prospects like Tiafoe and Black and Townsend will continue to mow down all comers and stoke hope for the next age of American competitiveness. And it will continue to be as hard as it has ever been to tell Americans, who hate randomness and crave explanations, what is almost certainly the truth about tennis: Our success is largely determined by chance and there is little we can do about it, except wait for the next gifted kid to come along.