Sonny Bill Williams is no longer the threat on attack that he once was.

OPINION: Sonny Bill Williams is starting to look like a very expensive mistake.

The old Newlands grounds has a buzz that makes any rugby player on the planet want to play and Sonny Bill wanted to play. The All Blacks were on the attack early on and Beauden Barrett went in to play halfback.

Sonny Bill eyed up the pass as it left Barrett's hands. He raised his hands to catch the ball and glanced away at the Springbok defenders. Only, a rugby ball is no respecter of reputation. It whistled through Sonny Bill's hands and biffed him squarely on the forehead. Sonny Bill is a hard man but guess who blinked first.

GETTY IMAGES Kieran Read and Sonny Bill Williams celebrate the win at Newlands.

Sad to say that clownish moment has been the story of Sonny Bill's season. He had a couple of great moments playing for the Blues against the Lions, but he is not the player of seven or even two years ago. Sonny Bill has lost a yard of pace, which he could ill afford to lose, and he has lost some of the agility that used to allow him to spin in the tackle.

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REUTERS South Africa's Malcolm Marx lines up Sonny Bill Williams.

Against South Africa he made tackle after tackle, although he was never able to get into a front-on position to make the kind of destructive tackle that defined him. He was always grasping at a man who was nearly past him. Sonny Bill made 23 tackles in the match, a heroic effort, but none of them made an impact.

The bigger worry for Steve Hansen and Ian Foster is that Sonny Bill is making little impact on attack any more. Yes, there were a couple of elegant passes as the All Blacks ran out of defence. There was also a lovely long, flat pass to Dane Coles. But these are the things you work on with Sonny Bill, they are not the reasons why you select him.

He is there to cause havoc in midfield. He is there to draw in defenders. He is there to make space for others. He is there to intimidate the opposition. But South Africa looked at Sonny Bill as an opportunity rather than a threat. They felt that he was a turnover waiting to happen.

And South Africa were right. Sonny Bill turned over four pieces of prime attacking possession in the first half. There was the ball that bounced off his bonce after five minutes. Then on 18 minutes Crotty nearly scored off a well-timed cutback ball. Sonny Bill, who had been a decoy, decided to pick and go on South Africa's line. A bad decision and a bad body position allowed Malcolm Marx to win a penalty.

Ten minutes later Sonny Bill straightened the line, but he didn't break tackles and his body shape was again poor. Same man, same result. Marx came in and turned over possession.

Sonny Bill has lost that bit of zip that would take him half through the tackler. He has lost the agility that allowed him to turn and pop up the ball for his support. In some ways of course it is a miracle that he is still playing at all.

When he ruptured his Achilles playing for New Zealand at the 2016 Olympics, many thought his career might be over. The surgeon certainly did not give much for his chances. It is a testament to SBW's professionalism and determination that he was able to do the rehab to make him a top-level player again.

Ah, but is he? Steve Tew must be wondering. New Zealand Rugby spent a lot of money on Williams last June. It was money that probably hastened the departure of Aaron Cruden and Tawera Kerr-Barlow so SBW came at quite a price, a figure that has been estimated at $2.5 million over three seasons.

Tew said, "This is another very important moment for New Zealand Rugby….We know our top players have choices regarding where they play their footy and for him to sign a three-year deal with us shows he is truly motivated and excited about the opportunity and challenge of being remembered as a great All Black.

"There is no doubt that he is a very special person. Since first signing with New Zealand Rugby back in 2010, he has made a significant impact, not only on the field but off the field as well. He is a huge star with particularly our younger fans and has been an inspiration to a whole generation of kids."

Hansen said, "It's great news for New Zealand Rugby. He is an extraordinarily gifted athlete. His recommitment will bring a stability to the midfield and will allow us to build a world-class centre combination."

And all that may have been true until Sonny Bill blew out his ankle, always a risk in signing on an older athlete. SBW now looks like a marketing tool who is unwilling, for perfectly justifiable ethical reasons, to even do all the marketing. Although I do wonder how he is prepared to blackball BNZ and not AIG.

Williams' playing value looks sadly diminished. It was he who threw away the ball that Nehe Milner-Skudder had to dive on, leading to the wrecked shoulder. Hard to blame Sonny Bill, but it did seem like collateral damage.

I suspect that Sonny Bill is now more valued for his professionalism and the example he sets to the younger players than for his actual playing ability. And it is hard to see that changing. Now that Wayne Smith has moved on, and with another year on the clock, Sonny Bill is unlikely to get any better.

Surely it is time to look at pairing Ryan Crotty and Jack Goodhue on the Autumn tour. The All Blacks like a strong man at 12, but there are other ways to play the game.