Without question, Juan Martin Del Potro's exhilarating victory Monday night over Roger Federer in the US Open final - the finest title match in New York in decades - signals the start of a new age atop men's tennis. The significance of his wins over both Federer and Rafael Nadal in the semis indicates the level of competition has truly entered a new phase in the sport. Yet still we're left to ponder that eternally sad and clichéd phrase - what might have been. If only Del Potro had come along a couple of years ago.

For too long the only man who could penetrate Sir Roger's hermetically sealed force field has been Nadal. The lefty's dominance of Federer has been well documented - he owns a career mark of 13-7 against Fed, including the even more impressive statistic of 5-2 in Grand Slam finals on three different surfaces. This has been, up to now, the only measure that a scant few tennis historians - including yours truly - have invoked to deprive The Roger of that tiresome and needless Greatest of All Time (GOAT) label. But aside from Nadal there's been no one else to rise up to that that arduous, some would say Herculean, challenge.

If one decides to take part in that thorny, some would say futile, practice of comparing players from different generations, a critical gauge has to be the depth of field one is up against. What should clearly not enter dispute is that prior periods in men's tennis had far stronger, and varied, competition. Whether it's Rod Laver, Pete Sampras, Bjorn Borg or Pancho Gonzalez (the generally agreed upon quartet of players who are in the GOAT debate of the modern era), all of these men faced stiffer and more intense competition from more than one player than did/does Federer.

This in no way diminishes the singular accomplishments that Federer has compiled. Several of his records, one can utter with a great degree of confidence, will never been broken, let alone approached - 15 Grand Slam titles; streaks of 10 and 7 consecutive Slam finals reached; 22 straight semifinal appearances in Slams. The numbers are by any measure staggering and ridiculous. The only missing ingredient to this perfect recipe is that rarest of tennis feats, a calendar year Grand Slam, last managed by Rod Laver in 1969 (and this was actually less daunting back then as there were only two surfaces, clay (French Open) and grass (the rest of them) in the Slams - hard courts didn't appear until 1978 at the US Open and 1988 at the Australian Open).

Yet one can play the game of conjecture and consider the possibilities if Del Potro - or anyone else - had joined the battle during Federer's prime. Imagine how much more formidable and wondrous Fed's accomplishments would seem if he had been able to wage battle against both the indefatigable champion that is Nadal and a player of such imposing force as Del Potro. Laver had the Australians. Borg, McEnroe and Connors had each other. Lendl, Edberg, Becker and Wilander fought it out concurrently. Sampras was up against Agassi, Courier, Chang, Ivanisevic and Rafter.

But we'll never know. And mainly because we are much closer to the end of Federer's career than most would want to acknowledge. Though he has vowed to play at peak form through the 2012 Olympics, it's hard to imagine that he can sustain his current pace. Though it'd be utter folly to doubt the genius' resolve.

The graceful champion spoke volumes, in words and gestures, during his post-match press conference on Monday night. The tears that were present in Melbourne in January after being blown off the court in the fifth set by Nadal - some would say selfish tears at that, as it deprived Nadal of fully basking in his achievement - were replaced by words that acknowledged he had no answers for Del Potro in the end.

And he was OK with it. Of course he was - because how can one top the perfect season that Federer had put together? Completing the career Grand Slam in Paris, besting Sampras' record of 14 Slam titles at Wimbledon, then getting married and becoming a first-time father to healthy twin girls has left Federer a happy and wise man at 28. Dare I utter that most dangerous of adjectives to professional athletes or artists, the one word that is anathema to progress and the hunger necessary to improve? Yes, The Roger is content.

And a contented Federer will likely translate to a permanent shift at the top of the sport in 2010 and beyond (and lest the eternally short memories of fans go unchecked, before he was injured, Nadal was the runaway number one player until the Summer of Roger). There's no way anyone can expect Federer to sustain that competitive fire with little else to play for. Even if he were to lose in the first round of every event he entered next year, it wouldn't leave a dent in his legacy.

Now, if the busy and happy Dad is able to summon up the competitive fire and appear to be as brilliant as ever then yes, we'll all be able to enjoy seeing Fed compete against the powerful Del Potro, Nadal and all the others. Even more satisfying however, this would give us all a little insight into what could have been if Federer were 24 and in mid-career, with more than one rival. That may be too much to ask. But maybe it isn't.

Whatever the case, the men's game hasn't been this rich and joyful to watch in decades. If Federer can continue at least near his current level and Nadal comes back healthy, as he is expected to, and Del Potro can add a net game to his scarily powerful ground attack (a truly awesome, fear inducing thought) and Andy Murray and Novak Djokovic finally live up to their potential then - well, either way, the GOAT debate may be settled once and for all.