Talking to the best American male tennis player of the past four years, you may get a sense that he is living the wrong fantasy. _“_Tennis is the sport I watch least,” John Isner said recently, at a hotel in Cincinnati, where he was resting before his last U.S. Open warmup tournament, the Western & Southern Open. “I might put the Wimbledon final on TV, but I’m not focussed on it. N.F.L., college football: that’s another thing. I breathe that stuff. The N.H.L., too. And the N.B.A. I play fantasy baseball. I’m a really big fan of the W.W.E. My middle-school to high-school years revolved around ‘Monday Night Raw’ and Shawn Michaels. He was my favorite. My friends used to do home wrestling videos: we’d go to the grocery store, get a bunch of cardboard you could fall on without hurting yourself. We’d light off the little firecrackers. I don’t know where those videos are, but I was horrible.” Isner still watches the W.W.E. today, he says, “just not quite as much.”

Plenty of top tennis players are eccentric, or at least showmen. Ilie Nastase’s antics are legendary, as are John McEnroe’s umpire-aimed theatrics (“You cannot be serious!”). Andre Agassi’s neon outfits and untamed locks (wigs, by the end) inspired a generation of tennis rebels. Novak Djokovic’s impersonations of his fellow-players and reported habit of bringing his poodle Pierre to every Wimbledon are worthy signs of weirdness for the world’s current No. 1.

Then there’s Isner, twelfth in the world at age thirty, bereft of the bizarre. He’s from Greensboro, North Carolina, the son of a builder and a real-estate worker. He likes dogs (“I have an English cocker spaniel named Magill”), classic rock (“Boston only made, like, thirty songs before they broke up, and they’re all unbelievable”), and fishing. If he is unusual among pros, it is because he watches fake wrestling, he is six feet ten, and he’s very tidy. Isner also went to college for four years, at the University of Georgia, and graduated—“I studied,” he said, “but I got a lot of my partying out.” This is true of perhaps only half a dozen men ranked in the top hundred on the A.T.P. tour. (The rest of them jumped to the pros shortly after receiving their drivers’ licenses.)

At U.G.A., Isner’s nickname was Grandpa. “I move slow,” he said. “It’s not that I’m late; I’m methodical. If I have to get ready for an eight o’clock dinner, I start at seven. I don’t shower for twenty minutes, I just take my time. I lay stuff out. Every night before a match, I pack my bag and put it in front of the door.… I guess I’m type A. It started when I became a homeowner. If I see a little dirt, the next thing you know I’ve got the handheld vacuum out; then I’m Swiffering the floors.”

Isner’s slow pace has one major exception, though: he is one of the fastest servers on tour, having once clocked 149.9 miles per hour in a match. At U.G.A., the sports-information director had a nickname for his serve, which he shouted from the stands: “Give ’em Big Bertha, John! Big Bertha!” Isner has aced opponents seven thousand one hundred and sixteen times in his career, including a record hundred and twelve times in a single match in 2010 (the longest match ever). Matches against Isner feature a lot of broken strings and long stares. Even watching him serve can be dangerous, as one spectator discovered in 2011. All of this is due to his height, which provides an ideal angle for sending the ball into the three hundred and seventy-eight square feet of his opponent’s service box (or, occasionally, elsewhere). The net is between three and three and a half feet high, while the ball is roughly eleven feet off the ground when Isner wallops it. That’s a lot of room to work with.

Some say he’s a one-trick pony. He doesn’t have much of a backhand or a net game. He can’t move well or rally long. But, as tricks go, his serve is a good one. “It was in college that I realized I had the serve,” Isner said. “I started to grow into my body and get stronger. I was serving in the one-thirty-m.p.h. range, and my opponents were utterly helpless.” They tried to mess with him: stand at the fence or inside the baseline, or bail out one way. “They still do that today. Sometimes they just let it go by. I’ve played Gael Monfils a few times, and if I’m up forty-love in a service game he’ll go to the back fence and do something goofy, like sit on top of it.”

Despite having perhaps the most-feared serve in the men’s game, Isner has not seriously contended for one of tennis’s Grand Slam trophies, which haven’t gone to an American man since Andy Roddick triumphed at Flushing Meadows in 2003. Just as vexing, an American male hasn’t been No. 1 in the tennis world since February, 2004, the dawn of Roger Federer’s reign: the Swiss usurped the throne for a record two hundred and thirty-seven consecutive weeks, and still guards the top three. While Serena Williams has absolutely owned the women’s game and the Bryan brothers have taken doubles by twin storm, American fans are still waiting for a successor to Connors, McEnroe, Courier, Sampras, Agassi, and Roddick—all former world No. 1s who have, incidentally, done little to promote Isner’s candidacy.

“I never played at a tournament with Andre or Pete,” Isner said. “I’ve never even hit with those guys. I played with Roddick, [James] Blake, and [Mardy] Fish when I was younger, kind of looked up to them. Now they’re almost all retired. So I’m sort of the elder statesman of U.S. tennis. It’s a little weird.”

Isner’s eight years as a pro haven’t been without achievement: he has been in the top ten twice, and he has won ten A.T.P. singles titles and plenty of money (eight million and counting). He’s beaten Federer and Djokovic and had match points against Andy Murray. But at the Slams that really matter—including the U.S. Open, which begins on August 31st—he hasn’t made it past the quarterfinals. He insists, though, that he’s still an overachiever.

“I’m twelfth in the world. In American tennis’s heyday, I’d be fourth. But I was never tabbed to be the next No. 1. No one ever thought that possible for me. I never thought it possible. I decided I wanted to play pro tennis at twenty-one and turned pro at twenty-two, just hoping to make a living. When I left college, only one person wanted to sign me. That’s the agent I’m still with today. No one else wanted to touch a four-year college guy who didn’t fit the blueprint for tennis success. I cherish being in this spot.” He adjusted his hat, which advertised a fishing company. “I think things go in cycles. It appears that a lot of the young guys coming up are very good players. It appears that American tennis is trending up. There’s a half dozen seventeen-to-eighteen-year-olds right now that are arguably the most talented group American tennis has ever had. Let’s see what they can do. Let’s see if they can get past me.”