Okay, it’s finally over. The much-hyped exhibition between Pete Sampras and Roger Federer was good fun, though I’m probably in the minority for thinking that the tennis was just ho-hum. But the New York fans ate it up, and if there’s one thing that this exo proved, other than the fact that Federer and Sampras both suffer from personality deficiency disorder, better known as PDD, it’s that there’s a huge audience for tennis at Madison Square Garden.

But let’s not dwell on the past. There’s a far more interesting drama in the real world of tennis. Federer—a.k.a. Mono Man—has come out and told the public that the reason he wasn’t playing up to snuff in Australia, the reason he lost to Novak Djokovic in the semifinals, and the reason he got out-classed by Andy Murray in Dubai, was because he had mononucleosis. It’s a nasty virus, which can derail you for months. Just ask Mario Ancic and Martin Verkerk; the former is still struggling to get back into shape, and the latter’s career tanked, in part, because of it.

Federer assures us that he’s 100 percent now. That’s a good thing for him, because the other players smell blood and are circling the game’s big kahuna. Djokovic, for one, said that Federer is vulnerable, and that he also fully expected Murray to win in Dubai because the Scot’s style of counter-punching has a way of driving Federer nuts. The buzz in the locker room is that many players are gaining on the world’s No. 1. Said Djokovic: "Obviously, when the time is passing you learn more and more, especially if you play him, so I think after those results in the last couple of months more players are believing they can win against him."

On the other hand, Federer assures his fans—and his opposition—that his sub-par performances of late had much to do with his condition and not the players on the other side of the net.

Let the head games begin.

Djokovic’s comments can be considered spot on, or the product of a cocky kid who’s no stranger to making bold, and sometimes borderline ridiculous, statements. Federer’s revelation about his mono can be taken at face value, or you can see it as a convenient excuse for a champion who’s not accustomed to feeling the heat. Remember the rule the old Aussies, such as Rod Laver, Roy Emerson, and Lew Hoad, lived by? If you’re fit enough to hit the court, you’re fit enough to play. Period.

Federer was uncharacteristically insolent during his press conference after losing to Murray a couple weeks ago. Instead of giving credit to his crafty opponent, he expressed dismay that Murray’s game hadn’t evolved much since the last time they played, at Cincinnati in 2006, which Murray also won. Federer also said that Murray would have trouble getting to the top of the men’s game unless he learns to attach and win points. Was that the mono talking?

However you decipher all of this, Djokovic’s point of view is the most interesting—and the most ominous for Federer. Once a champion’s patina of invincibility is rubbed off, he never gets it back. When Ivan Lendl finally broke through against a dominant John McEnroe, it was only a matter of a year before his Grand Slam title days were over. When Michael Chang took those ill-fated steps toward the service line against Lendl at the French Open, the stoic Czech would never be considered a menace again.

Looking at the Top 20, and certainly the Top 10, in tennis, what separates the players? Talent, hard work, desire, focus—all of that does factor into the equation. But I’d also argue that among the best players, it’s much more a matter of confidence that determines where they rank. Think of how many times the all-timers, from Bjorn Borg to John McEnroe, have won matches before they even step foot on the court. Their opponents just don’t believe they can win, and believing is much more than half the battle. Even if their opponents go into the match with the right, gung-ho attitude, it often only takes one break of serve or one missed opportunity for them to loose that sense of self-belief that they can actually beat the best player in the world.

By the same token, it doesn’t take much to shatter a champion’s confidence and embolden his opposition. I don’t think Federer has reached that tipping point yet, but he’s certainly put himself into a corner. If he’s beaten again by the likes of Murray, Djokovic, or Rafael Nadal, what then? Will he say that Mirka slipped him a micky?

Kidding, of course, as Federer is a class guy. He’s got some big events coming up, starting with Indian Wells and Miami, where he can gain points as a result of his losses last season, and then his focus on the French Open, Wimbledon, and the U.S. Open. But if he continues to lose matches that he was easily winning even a year ago, what will he say? Will any explanation fly? I’m fairly certain what his opponents will be thinking, and it’ll be bad news for Federer.