For most of the past 15 years, men's tennis has been involved in a large-scale, mostly fruitless exercise in forensics.
The question – How does one deconstruct Roger Federer's game?
No other top pro has managed to fully adopt his balletic style, in part because he continues to tinker with it.
Here at the U.S. Open, Federer is catching attention for a new wrinkle in his strategy. On his opponent's second serve, he will now occasionally rush in to the baseline and half-volley the ball back. Few other players will attempt it because it's a potentially humiliating strategy. It puts the returner in the uncomfortable position of having to complete a charge, regardless of what's coming at him.
"The good thing is that when you do it, you have to play committed," Federer said. "Whatever is committed in tennis is a good thing. That half-and-half always backfires, it seems like."
There's Federer's credo boiled down to four words: No half-and-half.
It's something a lot of people are interested in, not because they think it will change the game, but because it offers some insight into Federer's mind.
Why would he make this counterintuitive switch now? What's his rationale?
That's fairly obvious. Federer's genius is in doing things that should not be done. He's reached the tinkering-in-his-garage stage of his career. As such, trying to reverse-engineer his game is pointless.
Instead, as we reach the latter stages of his exceptional run, we might instead consider that the key to Federer is not physical or tactical. Rather, it's psychological.
On Thursday, former world No. 1 John McEnroe – the man who crowned Federer the best of all time before it was fashionable – was trying to get at the heart of it.
As he started out, he wasn't talking about Federer. But the Swiss is the end point of the Godwin's Law of Tennis – every discussion eventually winds back to him.
"People make this huge to-do that, say, [erratic misanthrope Nick] Kyrgios enjoys basketball more than tennis. Well, join the crowd, man. There's a lot of guys like us who like basketball more than tennis. I love basketball.
"Tennis is tough to love at times, when you're tearing your heart and soul out in front of people … you feel like you're naked. It's great when it's working, but it doesn't work that often."
McEnroe leaned back and spread out his arms, changing gears suddenly.
"Federer's the guy that I envy the most, because he loves it more than anyone I've ever seen. No matter what he does, he can shrug it off."
Here, McEnroe adopted a version of Federer's mittel-European drawl:
"'Well, you know, I lost the finals. I was up two sets to love and a break. There's always tomorrow'…" – McEnroe goggled for effect – "… I'd be [saying], 'Where's the Empire State Building?!'
"That's part of why he's lasted. I think he's the most beautiful player I've ever watched, but at the same time, it's the part of where he can just shrug it off."
For years, people have been trying to get Federer to explain what makes him special. As a general rule, great athletes are ill-equipped to describe what they do. Their abilities are instinctive. It's a little like asking the rest of us how we breathe so well.
For as long as he's been asked, Federer has been trying to tell people the secret.
In 2009: "When you do something best in life, you don't really want to give that up – for me, it's tennis."
In 2013: "When you win everything, it's fun. That doesn't necessarily mean you love the game more."
Just recently, when asked if he ever considers trying to protect his legacy by going out now: "That to me is so silly … I want to just play full-out and see what's left … I mean, come on. Who cares if you lose another 10 matches? I don't think it matters. Some people might read into that. And that's okay."
It seems trite on the page, but maybe it's just that simple. Federer is the very best because he has natural gifts, and has worked obsessively to develop them. Perhaps he also has a cognitive advantage – he wants to play, compulsively, but doesn't absorb setbacks the way other people do. Maybe his ease in losing is what makes Federer such a winner.
He gives some version of this explanation in almost every postmatch interview. When he wins, he shrugs and says he's happy. When he loses, he shrugs and says he's disappointed (though, as McEnroe points out, he never seems very disappointed).
On Thursday evening, Federer floated by Steve Darcis in the second round, 6-1, 6-2, 6-2. He was at his elegant best, somehow making a one-sided beating watchable.
After losing the Wimbledon final two months ago, he spent most of his postmatch presser reflecting on how much he'd enjoyed the tournament. He's 34. Everyone wonders if he'll ever get back to that point again. Everyone but Federer.
Even his place in the canon seems to mean very little to him.
"The game is bigger than any athlete we've ever had. It really is," Federer said. "It's going to be even greater in 50 years' time, 100 years' time."
This is not to say that he enjoys losing. Rather, Federer deals with that unavoidable side effect of competing with a level of perspective that is as unique as his game. He cares, while simultaneously not caring.
It's an odd way to think of it, but that really is the best definition of 'loving the game.' You want to play it so badly that you are unaffected by the result.
Maybe what Roger Federer should be doing postcareer is not training the next generation in how to play tennis. It's teaching them how to play life.
Cathal Kelly