In the best shape of his life, 29-year-old Mardy Fish gears up for what may be the best chance he'll get at America's Grand Slam.

From the outside, the Hotel de Sers is nondescript, a four-story building with a tiny sign on a quiet, ritzy Right Bank side street in Paris. But behind its thin glass entrance you’ll find a well-appointed and surprisingly spacious breakfast room and lobby. It’s clear, when you walk in, that the modest exterior signals discretion rather than anonymity. It’s a good place for people who don’t want to be distracted, and who can spend $600 a night not to be. It’s a good place, in other words, for a successful pro tennis player.

On a Saturday morning in May, the day before the French Open was set to begin, those first-floor rooms were eerily silent until two tall men ambled into them. One was Croatia’s Ivan Ljubicic, who took a seat in a corner and began to read a newspaper. The other, wearing a baseball cap, dark T-shirt, and sweats, was Mardy Fish. A few weeks earlier, Fish had become, for the first time in his decade-long career, the highest-ranked tennis player in the United States. More recently, he had also joined the sport’s most exclusive club for the first time: the ATP’s Top 10. Fish stretched his lean 6-foot-2 frame sleepily and yawned. It had been a long night.

“Our GPS was screwed up, so we spent an hour lost in Paris,” Fish says with a sigh as he sits down to breakfast: coffee, croissant and an omelet, nothing heavy for this recently converted health nut. Fish, his coach and a few others had driven in from Germany the night before, where the U.S. had trudged through a few frustrating days on clay at the World Team Cup in Düsseldorf.

Chalk it up as another misadventure in the Yanks’ annual spring slog across European dirt. The two-month stretch has thrown a wrench into many a promising American season, and it slowed Fish’s in 2011. A thyroid problem had “zapped” him, as he put it, at the start of the year, but he had begun to get his game in order during a semifinal run at Key Biscayne. Then it was on to Europe, where his momentum stalled in the mud.

“It’s a tough time of year for us,” the Minnesota native says in an unhurried drawl as he looks down at his expensive Parisian hotel coffee. “I mean, I’m dying for a Starbucks right now.”

Fish laughs and shakes his head. He’s a veteran and he knows the ins and outs of the tour grind. But he also knows that this is a special time for him. Only 12 months earlier, he had been ranked No. 97 in the world. At 28, after two wrist surgeries and a knee surgery that had been caused in part by the extra weight he had been carrying around for so long—in late 2009, Fish was on the north side of 200 pounds—he seemed on the slow but inevitable road to career oblivion. Now, after taking all the “bad stuff ,” all the pizza and soda and chips and beer and butter and oil, out of his house; after counting every calorie and watching every carb, he’s 30 pounds lighter and nearly 90 spots higher in the rankings.

“I want to enjoy this,” Fish says with the same determination that helped him turn his career around. “I don’t want to just put in the time and run through it from week to week. This is a big time for me, to be in the Top 10. I want to represent the U.S. well everywhere I go.”

Playing well everywhere he’s gone has been a problem for Fish in the past. He had the skills; everyone knew that. Even growing up with Roddick as a teenager in Florida, it was Fish, a teaching pro’s son, who was viewed as the natural tennis talent. But big wins, like his straight-set drubbing of Roger Federer in Indian Wells in 2008, would often be followed by first-round defeats. Spells of consistent play would be cut short by injury or surgery. Worst of all, promising runs at Grand Slams regularly ended in frustrated thoughts of what might have been. In 2008, he reached the quarters at the US Open and took the first set against top-seeded Rafael Nadal in front of a fired-up late night audience. But he quickly let the next set go, 6-1, and it didn’t take long for the next two to follow. Last year, Fish was playing the best tennis of his career coming to Flushing Meadows, when he found himself back inside Arthur Ashe Stadium in the fourth round against another top player, Novak Djokovic. Fish is still visibly frustrated by that straight-set defeat.

“That was before Novak went on his run,” he says. “I had a shot in the first set, but I didn’t win it. You have to take those chances against the top guys. At the end, I was like, ‘Can I have a do-over?’”

Fish knows the grind, and more than that he knows, after all of his injuries, his ups and downs, and his years of being less than his fittest, how few and far between those kinds of opportunities are. Despite his longevity and success at other levels of the sport, he has never reached the semifinals at the sport’s measuring sticks, the majors.

“Why haven’t I done better at the Slams?” Fish asks rhetorically. “It’s a good question. There’s the physicality of three-out-of-five, but I’ve always had a hard time concentrating for that long, too. Something would throw me off or bother me. It wasn’t just the physical stamina, it was the mental stamina, too.”

And it hasn’t just been Fish’s commitment to the physical part of his game that changed in the last few years. He credits much of his recent success to his marriage in 2008 to Stacey Gardner, a lawyer and former Deal or No Deal model. The old story in tennis was that marriage dulls a tennis player’s competitive edge. Fish says the opposite has happened for him, that having someone to play for has made him more committed to his career, and to the people who work with him. It wasn’t always that way.

“I’d been selfish over the years,” Fish said last summer. “It’s such an individual sport. That’s not the case anymore with [Stacey]. A lot of people want me to do well and put in a lot of work for me to be in that position. I realize that now.”

According to Fish, his wife, apparently not the high-maintenance model type, has made the biggest difference. On the road, “she’s the brains of the operation,” he says. “She helps with everything: plane tickets, restaurants, getting us the best room.”

If the players of the past allowed their rough edges to be dulled too much by domestic life, Fish has responded well to that smoothing out, both of his personal life and his life on the road. Maturity, rather than the rough ambition of youth, has served him better on court.

“I’ve tried most of all to bring a sense of calm and organization when I travel with them,” says Stacey, who has always been a sports fan. “I’ve been proud to see Mardy rededicate himself. He has such a different presence on court now.”

During their rare breaks from the road, the Fishes live in Los Angeles with their dachsund, Charlie. It’s been an adjustment. “I grew up in Minnesota and Florida,” Fish says, “and L.A. is just so different.” Fish says he doesn’t have time, when he is there, to do much more than catch up with friends and hone his already very accomplished golf game.

What Fish does more than anything in L.A. is work out at the USTA’s training center in Carson. There he shares a coach, David Nainkin, with his frequent hitting partner, Sam Querrey. In the last year, with his new body and new confidence in his stamina, Fish says he has finally, at close to 30, learned what he can do on a tennis court. “I’ve gained a half step, that’s the biggest difference. It makes it easier to defend, but also easier to get in and attack. Moving better opens up so many possibilities. I look at old pictures of myself and tell Stacey, ‘Why didn’t you tell me I looked like that?’”

But even a lighter, more dedicated, more confident and versatile Fish still hasn’t been able to avoid the pitfalls and setbacks of the grind. His superb 2010 ended in more frustration, with an injured ankle that hasn’t completely healed. And his loopy thyroid helped send him out in the second round at the Australian Open. (“That was a low moment,” Fish says.) But this is the life of even a successful tennis pro. Time is spent waiting, in quiet hotels in foreign cities, for your body and mind and motivation and maturity to be perfectly aligned so you can make the most of that talent you’ve always been told you have.

Fish said, as Wimbledon and the US Open approached, that he felt like all of things had come together. The Open in particular is a signature goal, not just because it’s his home Slam, but because Fish was a late-bloomer, as he has been with a lot of things, in his appreciation of Flushing Meadows’ special madness.

“I didn’t like the Open for a long time,” Fish says. “I’d never done that well. The atmosphere kind of stressed me, it was so fast-paced and noisy there. But I knew the surface was good for me, the fast hard courts. Now I love it there.”

What changed? Fish finally went to his best friend, Andy Roddick, a man who has thrived in that fast-paced atmosphere like few other players.

“I asked him, ‘What do you love so much about the Open?’ He said, ‘Play one night match, with that crowd behind you, and you’ll be hooked.’ He was right. When I played Rafa in ’08, even though I lost, it was like nothing I’d experienced on a court before. I want that again.”

Fish may soon get that chance. At 29, in the best shape of his life, with a career’s worth of experience and disappointment behind him, it may be the best chance he’ll ever get at America’s Grand Slam. He knows he hasn’t always made the most of the chances he’s been given. He knows that this is why he chose to dedicate himself to the game like he never had before two years ago. Fish knows, this time, that there won’t be any do-overs.

Originally published in the September/October 2011 issue of TENNIS.