With one simple announcement, all is well with the world champions. Which sounds a bit silly. How can world champions be unwell? 'Played like stink, and here we are, the best on the planet...' But this is England, and they are the world champions, and they are a bit poorly. And now they're going to be fine again. Because Jonny Wilkinson is the new captain.

For the champions, denied the services of their leading points-scorer, it has been a year of plunging fortunes. Five defeats in their last six games. But don't worry, cos Jonny's back. Rise, fall, rise. It's positively tidal, this period of English rugby history. But don't fret. Here's Jonny, shoulder nerves reactivated, to calm the motions, control the flow, cup the injured sparrow in his hands and set hearts a-flutter. Metronome and pin-up in one. He has a special place in rugby.

Can it all be so simple? Without wishing to drop guano on Nelson's column, I can't see it.

This time last year, Wilkinson was about to be plunged into a personal playing crisis. He went to the World Cup, for me, as the best outside-half ever to have played the game. His accumulation of points spoke for itself, he thumped the ball off either foot and passed off both hands with complete ease and accuracy. If, going solo, he lacked the gliding elusiveness of Barry John, the jagged side-step of Phil Bennett or the 0-60 of Jonathan Davies he more than compensated by being the most ferocious tackler in their position by a country mile.

At the World Cup the best player of all time fell to bits. Hell, it happens. He took half a step too far before clearing, he began to stutter on reception of the ball, his decision-making took him into heavy traffic. He buried himself in rucks, a lover of exposure - a naturist almost - seeking shelter in pit-pony darkness.

And as his game disintegrated he, as vice-captain, presented himself before the world and set about wringing his hands in public. No, he put his whole self through the mangle. He talked of the goals he set himself, the pressure he applied on himself, the anxiety he suffered.

By the time of the semi-final he was no longer flying solo at press conferences. He would be flanked by Lawrence Dallaglio and Martin Johnson. They looked like a pair of giant goons on either side of their flaky boss, purveying devoted respectfulness until a smirk broke out if Don Jonny threatened to go off on one, down martyrdom alley. They then gently steered him back to the task of playing France in the semi.

To be fair, he was rigour itself against the French. He outplayed Frédéric Michalak, who had been threatening to steal the whole World Cup show but whose collapse in the Sydney rain made Jonny look like a model of sturdiness. Wilkinson was back, in the nick of time.

Against Australia in the final, he of course dropped that goal. It was the moment of all time in the game of all time. But, to be honest, it was a simple kick. The pass from Matt Dawson may have placed him on the wrong foot, but the creeping set-up by the forwards had put him in exactly the right place. It was a bread-and-butter kick in front of the posts for a player who sends the ball over from the touchline for fun.

Wilkinson took his chance unerringly and the parades followed. But Stephen Larkham, his opposite number - and even while receiving running repairs to a nasty facial injury - played more authoritatively on the night.

So? Well, it just means that Wilkinson is not superhuman. For someone who is only 25, a lot of Jonny is already shrouded in myth, most of it deserved but some of which wraps him up in infallibility.

Not only does he have a track record of losing the plot, but after his mythical moment he was also out of the game for nearly 12 months. A year is a long time in the politics of pain and we do not know yet if his shoulder and neck are fully up to the demands of making Test tackles. He hasn't put them through trials at Newcastle yet. He is, as everyone who has witnessed his comeback observes, 'easing his way back into things', which I think is another way of saying he isn't finding it that easy to rediscover the mastery of his trade.

It hasn't prevented him from being fast-tracked to England. Barely back with his club, he has now been given the captaincy of his country. It is an appointment for the long term but it has triggered hopes of immediate fulfilment.

Here, we run into the second obstacle to instantaneous revitalisation. The England Jonny rejoins is not the England he left behind in Trafalgar Square last December with the cheers of a million ringing in their ears. You can hear the cruel fates chuckle: with one hand they usher Jonny back, with the other they twist the knee of Richard Hill. They give; they take away.

Hill may not be gone for ever from the back row, but he joins that list of heavyweights who will not be there to provide ballast aboard HMS Wilkinson. No Martin Johnson, Jason Leonard, Neil Back, or Lawrence Dallaglio. Such has been the form of others like Ben Kay and Steve Thompson - or such have been the injury fortunes of Phil Vickery and Trevor Woodman - that Jonny may have to peer hard through many bags under the eyes to make sure there are any of his old muckers left.

The point is, I suppose, not to expect too much too soon either from Jonny or his team. This may be uncomfortable for Andy Robinson as he looks to moor himself to the job of head coach all the way to the next World Cup. But the simple truth is that England look vulnerable up front and behind.

South Africa, as the new champions of the Tri Nations, will come to Twickenham in November with the robust clatter that is peculiar to them, while Australia will be more cerebral, without being exactly non-aggressive. In the New Year, the other five of the Six Nations will no longer walk in fear of being flattened by Johnson's pack within the first quarter of an hour. Kick off, ouch, game over.

The pain may flow the other way for a time. Since we are only at the start of a four-year World Cup cycle, it dos not matter. Myth Night II does not have to be made today. Before it goes into production in 2007, we may have to grow accustomed to the sight of Jonny Wilkinson playing the part of mere mortal.

You've read the piece, now have your say. Email your comments, be as frank as you like, we can take it, to sport.editor@guardianunlimited.co.uk, or mail the Observer direct at sport@observer.co.uk