David Leggat: Federer's slide raises question of when he should retire

It happens every time he does not win a Grand Slam, and the nay-sayers are growing in number when it comes to Roger Federer.

Forget that he's the greatest tennis achiever of them all. Seventeen major crowns make that point in capital letters.

But of late failure to win a big title is written down as the start of the end for the Swiss artist.

Now it's becoming a given. At 30 Federer is on the slide.

His failure to make even the semifinals at the US Open this week produced a collective shake of the heads from the tennis cognoscenti, taken as positive proof that Federer is now no more than simply one of the leading players in the game, as opposed to The Best.

Federer had been expected to ease past Czech Republic player Tomas Berdych. Instead the sixth seed cleaned Federer out in four sets.

Berdych is no pickle, but this is a sport where four men have ruled the court at the big events in the past few years - Federer, the injured Rafael Nadal, Novak Djokovic and Andy Murray, who remains, despite winning the Olympic final last month, the perennial Nearly Man.

That may change next week if he gets past Berdych in his semifinal.

Berdych can play, but has often butchered opportunities when it really mattered. Still, he didn't need to bring his A game to Arthur Ashe Stadium; Federer was that bad. Forty unforced errors tells part of the story.

In 23 previous night matches on the Flushing Meadow centre court, Federer had never been beaten; he's never failed to make the last four since 2003.

Last year, Federer lost a five-set quarter-final at his home away from home, Wimbledon, to Frenchman Jo-Wilfried Tsonga, having been two sets up. Unthinkable.

Before winning Wimbledon a few weeks ago, Federer had failed to win any of the previous nine Grand Slams, dating back to his victory in Melbourne in 2010. Nadal had won five, Djokovic four.

Here's a thought: using the age-old test, who would you have play a match for your life? Until beset by injuries, Nadal would have to have been among the first of choices.

Go back a generation and you might plump for the American, Jimmy Connors, who never knew when he was beaten.

But for sheer artistry Federer is the guy who puts more backsides on seats than any other player.

The question now becomes when he'll decide that settling for being among the elite is not good enough.

The hardest call for sports people, or anyone whose career at the top has a finite time span, is so often when to stop.

Andrew Strauss got it dead right last week when he retired from cricket. He had achieved all he could for England. Life moves on.

That's the decision facing Federer now.