Kelly: Gaël Monfils is the life of the party on and off court, win or lose

When he was 19 years old, Gaël Monfils found himself with some time to kill in Las Vegas. So, as one does, he entered a professional paddle tennis tournament.

Paddle tennis is to actual tennis what Ping-Pong is to squash. Or something like that.

Monfils, a three-time Grand Slam winner as a junior, had never played the sport. Three days later, he'd beaten the best player in the world and won the event. After his victory, he did a little dance and stood on his head.

"It's fun, but my principal sport is tennis," Monfils announced.

Which will be news to you if you've watched him since.

Monfils, 28, is a multisport prodigy and a gentleman often so full of Gallic ennui he ought to carry a baguette onto the court.

He trends so low on the Giving-A-Damn scale, he's essentially subterranean. He has the most dangerous gift for a sportsman with this tendency for mental drift – natural athleticism.

The Frenchman has bumped up and down the rankings over his career. He's been as high as seventh in the world. Right now, he's 24th. He should've won a bunch of things.

He hasn't won anything of consequence. Good news: This doesn't bother him in the least."It's not a job. It's a sport," he said after advancing to the quarter-final here. "Sometimes if I'm just fed up with that, just leave it … it's like, you know, I don't give a [crap]."

What makes Monfils fascinating isn't his shoulder-shrugging approach to the ATP grind, but the style with which he manages to screw things up. More than any pro I can think of, Monfils is a beautiful loser.

Everyone here will tell you he is the most physically precocious athlete on the tour, and maybe ever. Week after week, he covers more court than tarmacadam. He makes shots of such ridiculous ambition, his matches often come across more like exhibitions than competitions.

Early on here, he took a brilliant 110 mile-an-hour cross-court winner. In a completely Monfilsian touch, he leapt two feet in the air as he hit it. Why? Well, why not?

Everyone else is prattling on about restoring your electrolytes. Monfils drinks Coke at breaks.

He's also … how to put this nicely? … a bit cracked. He spends a lot of time screaming at his racquet, or people in his box, or the crowd, or himself. Most players who carry on this way do it to psych themselves up. It's a performance based on self-deception. Monfils gives the impression that he does this sort of thing alone in his kitchen.

The only thing separating him from global superstardom is a major title. There hasn't been anyone quite like him in the sport since that foul-mouthed, charismatic crackpot, Goran Ivanisevic, won Wimbledon as a wild-card entrant in 2001.

Since then, men's tennis has crested a wave of quality, but lost its personality. Novak Djokovic, who has the deflating habit of assuring you he's kidding immediately after telling a joke, is what passes for a cut-up.

Though no one is capable of copying his game, just about every pro over the past 10 years has mimicked Roger Federer's Zen presence, on and off the court.

When you see Federer backstage at the U.S. Open, he's always by himself. Other pros – even the fringe ones – trail entourages like thought bubbles. Federer does his own thing, schleps his own bags, signs a million autographs each day. This is his work, and though he approaches it with good cheer, it's also with a very Swiss sense of purpose.

Then there's Monfils, who attracts bodies like gravity.

On court, he seethes. Off it, no one is having more fun. He is always surrounded by other players, high-fiving or bent over laughing in a variety of languages. If he doesn't take his tennis very seriously, it's because he doesn't appear to take anything seriously at all.

Imagine how you'd behave if you got to be a great tennis player for just one day. That's how Monfils treats every day.

If winning is what separates him from the spotlight, Monfils is what separates Monfils from winning.

During his round-of-16 match, he entirely gave up on a game, wandering five feet inside the baseline on Grigor Dimitrov's serve. The Bulgarian looked up, baffled. Monfils roughly gestured for him to get on with it. He lazily pranged his return toward the stands. The crowd booed. Monfils continued to mutter to himself.

A great many players can win well. Only Monfils can surrender with such élan.

He has two general court gambits – lose games he should have won; win games he should have lost. The match against Dimitrov was the latter. It didn't occur to you that Monfils was playing well until he'd won. Monfils has yet to drop a set at Flushing Meadows.

He'll play Federer in Thursday's prime-time quarter-final. If he wins, this will be only the second Grand Slam semi he's reached in a decade.

Warily assessing Monfils's game, Federer noted that he should be a top-10 player, but for the fact of "not wanting to play sometimes because of reasons only he can explain."

Predictably, the narrative surrounding Monfils here is that of a player who may have finally figured it all out. Monfils rejects that storyline, somewhat confusingly.

"I think I'm the same. You don't understand why, but I understand. I'm cool. As usual. Still the same. Hanging around. No coach. I'm happy. Good."

And on the topic of effort: "I try my best for everything. But if I don't feel happy, I don't do it."

Let's hope he's happy on Thursday night, because tennis needs Gaël Monfils a lot more than Gaël Monfils appears to need tennis.