Let us be generous about Serena Williams' pullout from the Singapore WTA Finals. Let us show sympathy. But only just enough.

Let us admit that losing the US Open - and thus the Grand Slam - to a fringe player, when she was three-quarters way into history's embrace, must have been deflating.

Let us presume that tennis currently must not look like fun to Williams. The court a prison. The racket a wand with expired spells.

Play? For what?

It is heart-breaking.

Except that this is what sport does every day. It disappoints, devastates, denies. The golfer who fails to qualify for a tour by a stroke, the swimmer who loses gold by 0.01sec, the English defender Laura Bassett whose own goal knocked her nation out of the women's World Cup in the semis. Sport cries a river every month, which is precisely what makes it human and irresistible.

But heartbreak - and its associated afflictions which are disinterest, frustration and lack of motivation - is never a reason not to show up and play. Else grounds would be empty. Heartbreak isn't a condition written into the rules. Champions turn up because that's what a sport demands and what sponsors pay for and what spectators wait for.

Andy Murray, for instance, may have a substantial reason to skip the men's World Tour Finals - the Davis Cup final, on a different surface, is the next weekend - but he can't.

The scheduling is pitiful and if we wish to see the best of an athlete we owe him an environment which encourages it. And yet Murray - among the most interesting and empathetic of athletes - owes the audience his best efforts in both events.

Because this is the contract that professional stars agree on: They will be deified, not have to stand in line at restaurants, fly by private jets, own estates in every continent and generally be pampered in a proportion that has no connection to the real world. They take from sport and so they must give to it as well. By running for us. Week after week.

Even to Singapore.

Let us consider that there is scant criticism of Serena's decision to skip Singapore because injury and not heartbreak is the official reason for her rest. No precise ailment has been identified - which would be helpful - but at 34 her body must feel like a dinged-up race car. Already thrice this year she has withdrawn, from Indian Wells with an inflamed right knee, from Rome and Bastad with a painful right elbow.

Injury as an explanation adheres to the rules and does not offend logic. Except that just days before she pulled out her coach Patrick Mouratoglou spoke to EspnW and did not mention the words "heal" or "injury". Instead he said that "after this year and the three Grand Slams (she won), the question is how high her motivation is to play those (year-end) tournaments. I don't think she should play if the motivation is not really high".

So maybe absent motivation and heartbreak does have some bearing on her no-show. And yet, again, there is no censure because how do you question a woman who gives women's tennis life and is an astonishing advertisement for women's sport on a sexist planet?

And, yet, let us say this: Serena, nevertheless, should have tried to play in Singapore. Should have waited, almost till the event began, to be sure she couldn't play. Because tennis in the growing East needs her presence. Because if you're the best then you have the biggest responsibility to the game.

We hope she comes to Singapore anyway, even if merely to chat with kids and interact with fans. Because if she bypasses Singapore and goes straight to Manila in December for that big-money, noisy shindig called the International Premier Tennis League, people might raise an irked eyebrow. The IPTL is hardly physically challenging and she will have healed but it will look clumsy. Then again, perhaps she does not care how it looks.

Serena warrants appreciation, admiration, sensitivity but also perspective. As much as we applaud athletes for pushing their bodies, they are doing their jobs and chasing their dreams. No one is building a road in the sun here or spending all day cramped in a toll booth. Instead this is, in some cases, a very nice, high-definition way to make a living.

This year, for instance, Serena earned US$10,582,642 (S$15 million) in prize money. Last week, on the other hand, Olympic swimming champions turned up in town, a delightful band who wore smiles which did not fade into sulks even when half their World Cup was cancelled due to the haze. When they did race, all those hundreds of miles swum in practice now condensed to 100 competitive metres, they did so for scant reward.

Win a race, earn US$1,500. Hell, it was almost heartbreaking.