If Thorpedo can ditch his coach, is anyone safe?

You're a living legend and in the fast lane to becoming the greatest swimmer ever. At the last Commonwealth Games you won six gold medals, a silver and broke your own 400m record. You are canonised by the press and a walking talking advertisers' dream.

Your response? Of course. You sack your coach. "He was quite surprised when I told him," Ian Thorpe told reporters. "It was a difficult thing to do."

Probably not as difficult as it was for Doug Frost on the receiving end. Frost had been teaching Thorpe since he was splashing around in the pool as a nine-year-old . Under his close eye Thorpe has broken 17 world records and his feet have a rival only in Kylie Minogue's bottom as Australia's most famous landmark.

"He [Frost] taught me everything," said Thorpe. "Whatever results I've had to this stage Doug's made a larger contribution than anyone else has."

Yet still he is sacked. When someone as grounded and nice and courteous and consistently successful as Thorpe waves goodbye to his coach, just three months after that other incredible success story Tiger Woods moves away from his mentor, there really is nowhere for a coach to hide.

It is tough luck on the man or woman with clipboard and stopwatch but great news for everyone drawn to sport for its sheer drama. The punchline is, do not take your eye off the coach: he is the Bond girl of the piece, allowed some good lines and a decorative presence but, in the end, totally dispensable.

Bob Woolmer, who has coached South Africa, Warwickshire and Boland, says: "There is a shelf life for every coach. If you are somewhere for too long, then your players or player becomes used to what you have to offer and search for something new.

"Maybe the new thing will just be the old thing dressed up differently but the players will still see that as their saviour. Because once a player or team start to lose, people look for excuses and the coach is the No1 suspect."

David Leadbetter knows this better than most. He revamped the swing of a young unknown, Nick Faldo, and over 13 years took him to six majors. Faldo responded by sacking him through the post.

It must hurt. The coach has nurtured the precious charges, put up with their tantrums, suffered the same early-morning starts, watched them sulk and then seen them cash in and search around for something newer, prettier, more up to date. Often he knows more about their lives than the players' spouse or parents.

Imagine the petty jealousies, the secrets, the resentment. Shakespeare would have loved it, more so when it is family who are involved. Imagine his Elizabethan beard twitch in delight as he saw the spectre of Richard Williams's salt-and-pepper face peer out of the players' box at Wimbledon or the ogreish Mr Dokic rant at reporters or Mr Graf carted off to prison.

Of course coaches do get a chance to get their own back, through that old favourite, the book deal. Roy Keane might have called Mick McCarthy "a liar and an impostor" but Pat Cash did better than that.

He coached Greg Rusedski for half a miserable year. But quite how miserable we were not to realise until Cash decided to reveal all in his autobiography after the pair had split over a bitter dispute about money.

"The whole episode lasted a mere six months. It will take me many more years to wash the bitter taste from my mouth." Then the short, sharp kick in the teeth: "I'm also clearer in my opinion of Greg Rusedski as a human being."

Nigel Sears, one of Britain's most successful tennis coaches, says: "The one-on-one relationship is pretty intense. You can be hired and fired at will, so the situation works only on mutual trust and respect. You never know, when you start with someone, whether it will work. This is professional sport, so it is always on the knife edge."

The new person behind Thorpe is Tracey Menzies, who has already been branded "the 29-year-old art teacher". Her task is easy: just make the perfect swimmer even more perfect.

She should have her packed bags at the ready.