Williams will return to the Chiefs at the end of this year. He'll be in good nick - he always is - and he'll be able to make the immediate and dramatic impact the selectors hoped for last cycle.
If he could be rugby league's International Player of the Year in his return season after five years away from the code, he will most likely be back in the rugby groove quickly enough.
Australia, too, have a growth asset in Israel Folau. The former NRL and AFL star is not a secret weapon as such but his understanding of rugby will be so much greater by 2015 that he will pose an entirely different proposition to opposition defences. On the basis of what Folau could become, the Wallabies of tomorrow hold more fear than the Wallabies of today.
It's the remainder of the big five - South Africa, England and France - who present more complex recruitment puzzles. All three have their eye on new acquisitions but their impact is hard to predict.
The Boks are possibly the most intriguing; veteran lock Victor Matfield is coming out of retirement all fired up about the prospect of making a test return.
He's serious about wanting to play at the next World Cup, despite the fact he signed off from all rugby in October 2011 and will be 37 in May this year.
"I have played in three World Cups and won one," he told the Rapport newspaper. "In my view, the current Bok team is the best one ever and will take the trophy next year. I want to be part of that team. It would be absolutely fantastic to finally walk away from the game in such a triumphant manner and then turn my focus to coaching."
Matfield has completed a six-month conditioning programme. He'll be fit enough, good enough and, because he's close to Boks coach Heyneke Meyer, it's easy enough to see the big lock being recalled.
Nostalgia is a powerful force for selectors. His return could be inspiring. He could be a galvanising force for the Boks, an iconic player back in the fold, doing all the things that South Africans love - winning lineouts, hitting rucks, intimidating others.
On England's heavier grounds and with winter looming, rugby's traditional values of set-piece and forward domination may be the key to winning the next World Cup.
Maybe, though, such values will be important without being determining factors. For the past two seasons, all the rugged, crunchy bits of test rugby have been the ante rather than the bet.
The big games - think back to Twickenham, Johannesburg and Dublin last year - swung on little moments of individual skill. The biff-and-bash stuff was all largely even; the outcome shaped by a magic pass or elusive run.
It was the same when France played England this month in the Six Nations - they hammered each other for 79 minutes and then six phases of high-skill rugby saw the French score at the death to snatch a dramatic win.
Have the Boks misread the tea leaves in regard to the game next year and what will win the World Cup?
New Zealand and Australia are introducing dual-code, exceptional athletes with explosive power and outrageous ability. The Boks are going for a veteran lock who will give them more of what they already have.
Maybe the Boks are right - they were in 2007 when then coach Jake White predicted a long way out that an attritional mind-set, kick-chase, set-piece and big defence would be the foundations of the eventual champion.
Stories have emerged that Sam Burgess of the Sydney Rabbitohs is considering quitting the NRL at the end of this year to join Bath and make a bid to be part of England's World Cup squad.
The 25-year-old will have to find a way out of his existing NRL contract but, if he can, this time next year, England will have a 1.96m, 116kg, bruising athlete with which to work.
Coach Stuart Lancaster is publicly reserved about a potential switch by Burgess.
"Given the competitiveness of the squad we've got at the moment, any new player coming in would have to earn the right to play - as everyone else has done," said Lancaster. "They do that by playing high-quality, consistent, top-level Premiership rugby."
Privately, he'll no doubt be a little more enthused, as Burgess could give England yet more ball-carrying bite, an abrasive defensive presence and the mobility and skills to provide continuity and width.
France coach Philippe St Andre hasn't narrowed his attention on anyone in particular but may look to cap former Sharks halfback Rory Kockott this year.
The South African will be eligible on residency grounds and has become a major star in France, after driving Castres to the Top 14 title last year.
He'd provide the energy, direction and tactical control that the French crave from their No 9 and he may be the man who gives them greater flow and cohesion.
Can he transform them into world champions? Possibly, but 18 months out, Australia and New Zealand have the most potent and credible game changers.
Five potential game-breakers
Sonny Bill Williams (New Zealand)
The 1.94m, 110kg midfielder was arguably the best second-five in world rugby by August 2012 - before he opted to return to league. Has an incredible ability to offload and is a damaging runner when he backs himself to beat defenders. Is a bruising and clever defender and already has 21 caps to his credit.
Israel Folau (Australia)
Has found his rightful position at fullback and by October last year, was starting to fulfil his enormous potential. At 1.93m and 105kg, he can run through tackles but has the pace and agility to also go round opponents. A brilliant athlete, he has the aerial skills to be a supreme attacking weapon from cross-kicks.
Victor Matfield (SA)
The 110-cap Matfield was the world's best lock when he retired in 2011. Hasn't played for two years - which may be a good thing - and has undergone a major conditioning programme to prove his commitment and ability to still perform. Can unpick any lineout and doesn't complicate his role.
Sam Burgess (England)
Media speculation is growing that Burgess is looking to get out of his NRL contract and commit to rugby. Has all the physical attributes and no doubt the right attitude, too. But he would need to learn a new code and find the right position in a possibly unrealistic time frame if he is to feature at the 2015 World Cup.
Rory Kockott (France)
A live wire halfback who often caught the eye in Super Rugby when he was with the Sharks. Has been a major star in French rugby since he joined Castres, where his tactical generalship, speed and strength around the ruck have been damaging.
