On Wednesday, having just endured the indignity of living out the grim forecast of her collapse, she looked in a sense relieved when the game, and her tournament, was over.

Certainly the nasty thing about choking is how obvious and irrepressible it is. Like drowning with an audience, it's preferable to everyone when it's over.

She looked at ease, charming even, when admitting that her tournament was finished and that, yes, she had ''choked''.

Her demeanour was disarming and it needed to be. At times she looked stricken on the court, tight in the face as if she'd seen a ghost. Maybe she had. The grand slam title-winning Stosur appeared on court in the second set and then flitted away in the third.

The irony of choking is that it punishes the choker for caring too much. After all, caring is what the sportsperson has forever been promised will make him or her better. But when an athlete reaches high performance like Stosur has, the caring part is mostly assumed in the rhetoric of sports psychologists, and the answers are sought thereafter.

Experts of any kind make their adjustments in minutiae. So the struggling sportsperson, rather than make wholesale changes, is offered confusing solutions such as, ''you need to give yourself permission to win''. At any rate, there is an apex in all anxieties at which a person either recovers or breaks down, but not necessarily in that order. It's the squeezing tight and then the letting go.

It happens everywhere. Golfer Kenny Perry was leading the 2009 Masters when he settled over the ball for his chip to the 18th green. He became so concerned with hitting his ball cleanly that he was ''unable to control his right hand on the club''. He choked and lost the tournament having had, as they say, one arm already in the green jacket.

Tellingly, he expressed later the unformed words that took him over during play: ''Great players make it happen. Your average players don't and that's the way it is.''

Stosur's case, as Sunday Age columnist Tim Lane predicted last week, has had the misfortune of sharing the stage this week with its antithesis in Bernard Tomic. His flippancy on the court is comical but you sense it helping his performance. Different to Stosur, his is the case of the talented underdog, arguably the period of a sportsperson's career that they may one day reflect was the easiest to occupy.

Notable among their differences is that Tomic, unlike Stosur, has no tact in his interviews. In other words, he scarcely edits his speech. This is a sign of a person who is not in doubt. Others might take it as a sign of something else. Either way, Tomic's looseness makes him compelling to watch during play in a way that Stosur is not.

It can be revealing to hear and see the gestures of sportspeople when they are not in play. In an interview they can sometimes elicit the opposite emotion from their audience than they do during play. Stosur and Tomic are two of these people. Roger Federer isn't.

It must be lonely on the tennis court too. There are no others to disperse mistakes among; every conversation is with yourself and there is much more time in a tennis match spent in thought than in play.

It is clear that being overly thoughtful during sports is not usually helpful to a player. We can say that someone is a ''smart footballer'', but we may also concede that they are not really thinking at all, only reacting intuitively as things happen.

Ernest Hemingway used to say of the intelligent matadors that they had too much imagination to be brilliant with the cape. What he meant by this was that the thinking man could imagine himself on the bull's horns and this made him timid, full of half-steps and vagaries. Because he was over-cautious, the bull always caught him.

The thoughtful person will always be told not to think so much, and the thoughtless person will always be accused of carelessness. This is inescapable and somewhere within this paradox is the key to success.

On Thursday, Tomic did something instructive of his form. Sitting down between games, he was drinking when the umpire called ''time''. Hurrying to screw the lid on, he dropped it and watched as it rolled out onto the court and arced back towards his foot.

He looked at the lid, shrugged his shoulders and walked on to win the match. I thought of another player of some success who might have twitched at this violation of routine, but try telling Rafael Nadal that he needs to relax. Stosur's coach, David Taylor, said it on Wednesday: ''There's no magic dust.''