OUCH! World champions and current Tri-Nations champions South Africa have come down to earth with a bump.

Halfway through this season's southern hemisphere competition, they are winless and pointless.

Around a year away from the big global event, they are all but hopeless.

Never say never, and all that, but at this point in time it's hard to imagine the Springboks being in the frame to defend their title in Auckland next autumn.

Like all the other winners of the Webb Ellis trophy, the Springboks, it seems, have hung on too long.

In doing so, all of them have not so much been victims of the "if it ain't broke, don't fix it" school of thought as unable to find a convincing answer to the question "why change a winning hand?"

No coach has yet had the courage to change a winning combination, and few players – Martin Johnson is the obvious exception – have resisted the temptation to grab at the chance of yet more glory.

It's difficult to blame either of them.

But the former are finding that while they are marking time, other coaches, teams – and even the law-makers – are changing the parameters by which the game is played – and the latter are finding, increasingly, that time waits for no man.

The new kids on the block are stronger, fitter, faster, hungrier – and, of course, younger.

Champions have a commodity that is nearly as valuable as youth – and that is experience. The knowledge that they've been there, done that, got the T-shirt and not just survived but emerged victorious counts for a lot but leaves them vulnerable to a one-off performance from inspired opponents.

First champions New Zealand ran into an Australian side in the 1991 semi-finals that was not only surfing on the genius of David Campese but, perhaps even more importantly, firmly believed that the force was with them.

The Wallabies, in turn, fell foul of a last-minute Rob Andrew drop-goal in the 1995 quarters, and a last-minute Jonny Wilkinson drop-goal in the 2003 final, while South Africa succumbed to the same form of execution when Stephen Larkham produced something improbable in the 1999 semi-finals.

England, surprised to reach the 2007 final, were squeezed off the park by the South African side which now props up the Tri-Nations.

The fact that both Australia and England came within a whisker of retaining their world titles suggests that the doctrine of continuity has a lot going for it.

The circumstances of their appearances in a second successive final make the argument a little less clear-cut.

In 2003, Australia produced a semi-final of such sudden and unexpected brilliance against New Zealand that they even surprised themselves.

In 2007, England produced not one but two undreamt of performances to overturn the Wallabies in the quarter-finals and the French in the semis.

The lack of strength in depth in the world game doesn't help.

There have only been four names on the Webb Ellis trophy and none of them should have the slightest problem making it through to the knockout phases each time. From that point on, there are only three knockout matches to negotiate and the accepted wisdom is that anything can happen when it comes to sudden death.

Subconsciously, perhaps, reigning champions have a different mindset.

Knowing that rugby immortality will be theirs if they get those three games right, they focus less on the process of development and more on the need to get to the knockout stages in one piece. The margins are tiny, but then they always are in top class sport, but if each member of a squad has a one per cent drop-off in terms of concentration, application or desire, the collective effect can be huge.

South Africa won the World Cup on the back of an aggressive defence, a dominant line-out and a fierce and unrelenting physicality.

Now, other sides have worked out how to pick holes in that defence and negate the power of the line-out, while, as a spate of yellow cards has highlighted, referees have started to find fault with the Springbok approach.

The coach is under fire as well and, knowing that victory in South Africa's three home matches in the Tri-Nations is imperative to restore pride in the eyes of an unforgiving public, Pieter de Villiers is unlikely to take a punt on any newcomers. Don't bet against the Boks finishing the Tri-Nations with a 50-50 record. Do bet against them retaining the World Cup.