Perhaps we will discover there was something wrong with Nonu, some twinge, or that he was still suffering after illness meant he was a late arrival at the tournament. Perhaps it was a straight swap, a chance Hansen and his cronies saw to change up some of the work, perhaps it was a blurred combination.
SBW has been out of work for some time since his unconvincing production against the Wallabies in the opening Bledisloe Cup in Sydney. Some hip pointer injury or leg problem then gave him grief in a season where he has not strung together too many strong matches.
His 26-test All Black career, before yesterday, has been mixed with some strong showings, others indifferent, a range of positional changes and contractual shenanigans. There have been moments of grandeur then the fadeouts with uncertainty about whether Williams can really cut it when the heat is on and the demands are at their highest.
When he strode on to Wembley after 45 minutes, the All Blacks were clamped in a massive battle. They were being squeezed and pressured, were 12-16 down and the crowd of 89,019 and surely some of the voices inside their heads must have been chattering about the chances of defeat.
The waves of blue and white hoops heat-seeking the ball on defence, then providing inquisitive matches with their attack, were unrelenting. The Pumas had the whiff of an upset in their nostrils and they liked that smell.
They could also see the flickers of uncertainty in the All Blacks' eyes, the raised looks for contact rather than concentrating on possession and the continuing error rate from the Cup favourites.
Enter SBW, the 30-year-old cross-code convert who played every game at the 2011 RWC but started in only three of the seven - twice at second-five and once on the wing.
This was an early change, especially replacing Nonu, who is the rock of the backline. But the All Blacks needed a boost. Straightaway Williams pushed down the blind, attracted two defenders and flipped a backhand pass to Nehe Milner-Skudder with the line open. The new wing can give 'em but this time he couldn't take it and the try was lost.
On the other side of the ruck, Williams surged through. His running lines were strong and offloading instincts were creating worries for the Pumas' defence, which had been solid. There was even a kick to relieve pressure.
It was longer than a cameo, which will do SBW and the All Blacks plenty of good. They've grabbed his attention and he responded. Now both parties need to nurture that harmony to bring more fruit to the All Black table.
