Shouldn't Roger Federer just bow out gracefully?

The Swiss is slipping from the heady terrain he used to inhabit and if he keeps falling it will tarnish his golden image

A picture of Roger Federer is normally one of the most prominent on the posters and his name is usually in the biggest type on the billboards, but the promoters of men's tennis might soon have to start rethinking their publicity campaigns. As the greatest player in the game's history prepares to celebrate his 32nd birthday next week, the signs are growing that his star is increasingly on the wane.

Unless the Swiss recovers his form in the last three months of the current campaign there is a very real danger that he will not make the line-up for the Barclays ATP World Tour Finals in London in November, which would be the first time for 12 years that he has not featured in the sport's season-ending finale. The year's eight most successful players – in ranking points won – form the field at the O2 Arena and Federer lies sixth in the "Race To London".

The next five weeks, as the North American hard-court season reaches a climax, are likely to be decisive and the omens are not looking good for Federer. A back injury has forced him out of next week's Montreal Masters, where nearly all the leading men are due to return to competition. He will hope to return at the following week's Cincinnati Masters, while the year's final Grand Slam tournament will start in New York in 22 days' time.

Several other players are snapping at Federer's heels in the chase for places in London and the world No 5 could easily be squeezed out. Since winning a minor grass-court tournament in Halle in June, his form has been woeful. Federer lost in the second round at Wimbledon to Ukraine's Sergiy Stakhovsky (world No 116), in the semi-finals in Hamburg to Argentina's Federico Delbonis (No 114) and first time out in Gstaad to Germany's Daniel Brands (No 55).

The simple fact that Federer played in those latter two tournaments tells its own story. The period immediately after Wimbledon is usually a time when the top players rest after the hectic clay and grass-court seasons before returning to competition in Canada. This was the first time that Federer has played in any tournaments – other than the Olympics – between Wimbledon and North America since his last appearance in Gstaad nine years ago.

Hamburg and Gstaad are both clay-court events and would have been of limited use if Federer wanted to find form ahead of the North American hard-court campaign. Unless he was trying to boost his bank balance – Federer can command appearance fees in excess of £500,000, though such sums are barely significant for a man who has earned $77.7m (nearly £51m) in prize-money – the suspicion is that one of the reasons he played was simply to boost his tally of ranking points in the build-up to London. However, he earned just 185 points from the two events.

Having scratched his way to the semi-finals in Hamburg, dropping sets to Brands and Florian Mayer along the way, Federer was then denied a place in the final by Delbonis, a qualifier. It was the second tournament in a row in which he had lost to a rank outsider, his defeat to Stakhovsky at Wimbledon the previous month having been his first loss against a player ranked outside the world's top 100 for eight years. When Federer went on to fall at the first hurdle to Brands in Gstaad, he left the tournament with a cheque for just €7,100 (£6,189), his lowest prize-money since he earned $9,000 (£5,937) following a second-round loss to Guillermo Canas in Indian Wells in 2007.

To add to his woes, Federer has suffered with a recurrence of the back trouble which has dogged him in recent times. He had to take anti-inflammatory drugs in Hamburg and will be anxious to recover in time for Cincinnati – where as champion he has 1,000 ranking points to defend – and New York.

The impression that there has been an element of desperation about Federer's tennis has been underlined by the fact that he has been experimenting with a different racket. Having spent almost his entire career playing with a 90-square-inch frame, since Wimbledon he has been trying out a 98-square-inch model. Federer said he had been contemplating a change of rackets for a long time but had never found time in his schedule – until his early exit from Wimbledon this summer – to test different equipment.

Federer has always insisted that retirement does not enter his head – he has talked about competing in the 2016 Rio Olympics – but if his recent rate of decline continues, might the Swiss reconsider his future?

Knowing when to stop is always one of the most difficult decisions for any athlete. There are plenty of top players who continued competing long past the age Federer is now – Jimmy Connors reached the US Open semi-finals at 40 and Andre Agassi was a US Open runner-up at 35 – but there are many more who put away their rackets earlier. Pete Sampras, Federer's boyhood hero, played his last match, winning the US Open, just after he had turned 31.

Will Federer still want to be playing if he falls outside the top 10, the top 20, even the top 100? He would still be a big draw and would still make good money from appearance fees and other commercial activities, but there is a danger of the former world No 1 tarnishing his golden image. It already seems strange to see the Swiss at No 5 in the world rankings – he dropped to his lowest position for 10 years after Wimbledon – and further falls will be inevitable unless his results pick up.

Until now quality, not quantity, has been at the root of Federer's success. He has always managed his schedule carefully, ensuring that he is at his best at the biggest events. He has won 77 titles in his career, but has never looked likely to pass Connors' record of 109. The Grand Slam tournaments have been at the heart of his work: nobody can match his total of 17 singles titles (Sampras is the next best with 14), while his record of 36 consecutive appearances in Grand Slam quarter- finals, which was ended by Stakhovsky, is likely to stand the test of time.

That Wimbledon loss, which was his earliest at the All England Club since his defeat to Mario Ancic in the first round 11 years ago, broke through an aura of invincibility at Grand Slam events that had looked in danger for some time. Federer's 2012 Wimbledon triumph had ended a run of two and a half years without a Grand Slam title and has been followed by some sobering defeats: a quarter-final loss in four sets to Tomas Berdych at the US Open; a five-set defeat to Andy Murray in the semi-finals of the Australian Open; a three-set drubbing by Jo-Wilfried Tsonga in the French Open quarter-finals.

The US Open, which Federer won five times in a row between 2004 and 2008, was one of many arenas where the Swiss used to reign supreme, but such is his recent decline that he is only the fifth favourite in most bookmakers' lists – behind Novak Djokovic, Murray, Rafael Nadal and Juan Martin del Potro – to win the tournament next month. The idea of Federer as an also-ran is not an easy one for observers to get to grips with; whether it is a concept that the great man himself will be prepared to accept remains to be seen.

When to go? Past examples

When some of the greats of the recent past have bowed out

Bjorn Borg (Last Grand Slam tournament: 1981 US Open) Aged 25

Stefan Edberg (1996 US Open) 30

Pete Sampras (2002 US Open) 31

Boris Becker (1999 Wimbledon) 31

Mats Wilander (1996 French Open) 31

John McEnroe (1992 US Open) 33

Ivan Lendl (1994 US Open) 34

Andre Agassi (2006 US Open) 36

Race to London: Current standings

The eight places in the field for the Barclays ATP World Tour Finals at the O2 Arena in November go to the players who have won the most world ranking points in 2013. These are the current standings:

1 Rafael Nadal (Spain) 7,010 pts

2 Novak Djokovic (Serbia) 6,230

3 Andy Murray (Britain) 5,160

4 David Ferrer (Spain) 4,440

5 Tomas Berdych (Czech Republic) 2,775

6 Roger Federer (Switzerland) 2,695

7 Jo-Wilfried Tsonga (France) 2,455

8 Juan Martin del Potro (Argentina) 2,370

9 Stanislas Wawrinka (Switzerland) 2,150

10 Richard Gasquet (France) 1,855