THE question drew an irritated response.

The 24-year-old Scot’s absences through wrist and ankle injuries have given the impression that the world No.4 can be fragile but the record shows he is a battler who is reluctant to quit on court.

Murray took his 18th professional title by winning the Cincinnati Masters at the weekend after Novak Djokovic, the 24-year-old Serb, retired because of a shoulder injury. It was the latest in a long line of retirals by the world No.1 and added to his reputation as the true hypochondriac of the tour.

The truth, of course, is that all the top players are carrying injuries as the final grand slam of the season approaches. The world tour does not quite march on Flushing Meadows but approaches the concrete jungle with a limp and a wince.

However, it is fascinating to search through the careers of the top four players and discover just who calls it quits and who has to be carried off on his shield.

Murray and Roger Federer are in the vanguard of the brave squad. The Swiss player has never walked off during a match on tour. Federer, most notably in his quarter-final defeat to Thomas Berdych at Wimbledon in 2010, has used injury as an excuse but he has never taken the ultimate stepping of calling a halt to one of his matches.

It is one of the aspects of Federer that sometimes escapes scrutiny because of his peerless shotmaking but the grand slam record holder is a tough hombre.

This has increased his scorn for those who do not find the same resilience in moments of discomfort.

After the contretemps with Richardson, Murray said: “If you watch a lot of tennis you can see how much guys get trainers out on court for treatment. They did a study on it in Miami a few years ago and me and [Roger] Federer were the least for getting trainers out and pulling out of matches by quite a long way. If I feel something it’s because it’s there, not because I’m a hypochondriac.”

Murray also battles through injury, most notably at the French Open this year when he defeated both Michael Berrer and Viktor Troicki on one leg after he suffered an ankle injury against the Frenchman.

Of the top four, he is the second most resilient player behind the remarkable Federer.

Rafael Nadal, most regularly referred to as the tough man of tennis, has a history of retiring in tournaments (see panel) but his most controversial habit is to call a trainer for treatment.

He was criticised for asking for treatment when struggling against Philipp Petzschner at Wimbledon in 2010. The German was sceptical of the validity of the injury to the Spaniard. The intervention of the medical team was certainly followed by a breakdown in the rhythm of Petzschner’s serve.

Nadal also called for medical aid in his battle with Gilles Muller at this year’s Wimbledon and was again accused of gamesmanship but he was subsequently vindicated when it was revealed he had broken a bone in his foot.

Djokovic, now the king of tennis, is undoubtedly the master of the tennis retiral. He has pulled out with everything from gastroenteritis, cramps, dizziness, blurred vision and heat exhaustion.

“I’ve got to feel good because [Djokovic] has got about 16 injuries,” Andy Roddick told the crowd in an on-court interview at the US Open in 2008. Asked about an ankle injury affecting the Serb, his opponent in the next round, Roddick said: “Isn’t it both of them? And a back? And a hip? And a cramp . . . bird flu . . . anthrax. SARS, common cough and a cold.”

Djokovic extracted a measure of revenge by beating the American but his reputation as someone who would retire with a blister -- and he has -- persisted until he changed his training regime, diet and mindset.

The world No.1 suffered from allergies and was prone to dramatic drops in energy levels when playing in high temperatures.

The change from a whimperer to a strong man of the sport can be traced back almost a year to the US Open. Djokovic was struggling badly against his compatriot Troicki in 100 degree temperatures at Flushing Meadows before rescuing the match, then beating Federer before falling to Nadal in an excellent final.

Djokovic took heart from his performance and was energised by a gluten-free diet and a refined training programme. He then won the Australian Open and went on a winning run that has only been dented by Federer in the semi-finals of the French Open and Murray in Cincinnati.

He heads to New York with a question mark over his fitness but the odds are that he will able to make a tilt at US title.

Murray, on the back of an impressive tournament, now becomes a fancied contender for the US Open but the surest bet is that Federer, now 30, will not walk away from court through an injury short of amputation.