It is one of the most oft repeated clichés in football punditry that, "form is temporary but class is permanent."

We live in interesting sporting times. Roger Federer has only recently ended an 8 month spell without a tournament win, Tiger Woods is experiencing an even more severe drop in form and the South African rugby team have gone from only 1 defeat in 6 games during the 2009 southern hemisphere Tri Nations tournament to only winning 1 game in 5 so far this season. Speaking of South Africans, Kevin Pietersen has this week been dropped from the England cricket team after a string of distinctly below par performances this summer.

In Formula 1 we are witnessing a similarly perplexing failure to launch from Sebastian Vettel. Many in the (British) media and on their associated message boards are already decrying him as an overhyped crash merchant who can't make a decent overtaking move. But hold that thought while we revisit the illustrious sportsmen mentioned above.

Statistical process control is an important part of managing any manufacturing process and the opening quote expresses the difference between a short term rolling average and a long-term trend.

Roger Federer is a perfect example of the point. When he dropped to number 3 in the world following Wimbledon this year, it was the first time he had been ranked that low since 2003. Now he has won a tournament again, is back up to number 2 in the world and on Tuesday executed the most audacious shot in tennis playing the ball through his legs while running down the court. Not only did he keep the ball in play, he did so with such precision that his opponent had no answer and lost the point. What is more, during a journey into unfamiliar territory for one to whom winning usually comes easily, he demonstrated a different kind of class by emphasising the quality of Berdych's performance in dispatching him from Wimbledon in the quarter finals and making no mention of the injuries we later learnt were plaguing him.

The story of Tiger Woods in 2010 has come to be dominated by off-course events and these have no doubt had an impact on his performance. He would have to have been inhuman for such a level of upheaval in his personal life not to have an impact on his professional life. Such is his dominance of golf that despite having a season to forget he is still ranked number 1 in the world. It is too early to tell whether his first round 65 and fourth round 67 at the tour event in New Jersey over the same weekend as the Belgian GP signifies a turning point but it certainly feels like it.

The South African rugby team's poor form this season is more inexplicable than that of either Federer or Woods. This is substantially the same team which dominated the Tri Nations in 2009 and the Rugby World Cup in 2007. Sure, the SA rugby authorities made the bizarre decision not to renew the contract of the coach who led them to world cup glory but the incumbent has been in place since the end of the 2007 Rugby World Cup. Whatever the root cause of their poor season the long-term trend shows us that South Africa, like their Australian and New Zealand rivals have a habit of coming good more often than not.

Since jumping ship from South Africa to pursue a more lucrative career in England (something this writer can identify with) Kevin Pietersen has built a career batting average in the 5-day game of 47.8 runs. Only 13 active players enjoy greater career averages. This season, though he has only managed a paltry 33.8. Does this recent run of form mean that he is suddenly a poor cricketer. Not for a moment. He expressed his obvious disappointment via the ubiquitous medium of twitter, albeit more robustly than might have been advisable, and by all appearances is taking the opportunity presented by a loan spell at Surrey to get his eye back in.