It was probably no surprise that the result of Monday's US Open final was reported just as much as a Roger Federer defeat as it was a Juan Martin Del Potro victory.

Such has been Federer's dominance that virtually any defeat for the Swiss is regarded as a shock.

Yet for how much longer will that be the case?

Clearly it would be crazy to write Federer off as a spent force after a narrow loss such as this, but you have to wonder if a new era is dawning in the men's game.

Prior to Monday, Federer and Rafael Nadal had won 16 of the last 17 Grand Slam titles.

Such statistics seemed to intimidate many of their opponents during that spell; plenty seemed beaten before they even stepped onto court.

That mental edge can surely not be as great now.

The rest of the tour will surely have expressed delight, at least privately, at how Del Potro first battered Nadal and then managed to turn around the final with Federer at Flushing Meadows.

At the very least, the door is now ajar - not just becasue of Del Potro's feat. Whether the chasing pack can push right through remains to be seen.

The fact is Federer is not getting any younger - he's now 28 and it's rare for 30-somethings to be at the very top of the game. Andre Agassi was very much an exception to the rule.

Age may not appear to be taking its toll just yet, although it should be noted that Federer did not impress in the deciding set of either the Australian or US Open this year.

As for Nadal, his crushing defeat in the semi-finals in New York had people talking about his injury problems once more.

His year has been blighted by injuries. It was no surprise to long-term Nadal followers that his knees finally became too painful for him to play earlier this summer. Now you wonder whether the abdominal strain could be related.

I'm no doctor, but it's well known that is trying to compensate for a weak part of the body it's easy to put strain on others.

Certainly Nadal has looked leaner since returning from his knee absence. It could be a factor.

Again, Nadal is too good a player to write off - the tennis he played at Wimbledon 2008 and January's Australian Open is some of the best I've ever seen - but again there are signs that Nadal's best days could be behind him.

I hope not, but I doubt Del Potro shares my view. Neither will Marin Cilic, another youngster with a power game that looks set to trouble the best in the coming months and years.

His display against Andy Murray was simply superb and while he could only keep it up for a set and a half when he met Del Potro in the next round, Cilic will be there or thereabouts in the future when it comes to the big prizes.

Of course, Murray himself will be hopeful of getting in on the Grand Slam act, while Novak Djokovic, the same age at 22, seems too good a player not to win another major.

One thing is for sure, it will be interesting to see what unfolds in 2010.

Do you agree with Andy? Is the Federer-Nadal era of domination over? And if so, who can fill their shoes? Email your feedback to tennisfeedback@sportinglife.com.