For a player who has forged his legend through spectacular finishing, the script is all written for this afternoon's international farewell.
This particular Shane will not ride off into the sunset; he will jink, hop and sidestep with Wallabies fumbling in his wake and Wales toasting the perfect send-off.
That's the romantic view anyway. Of course, the reality maybe somewhat different, especially when one considers Wales have only won once against Tri-Nations opposition in their last 14 attempts. They will require Williams to be at his twinkle-toed best to prevail. Yet, more than that, they will need to show the same collective creativity and physicality which carried them so far in the Rugby World Cup.
However, to regard Williams as merely one in 15 today (or in modern parlance, one in 22) is to rival a Dalek for sentiment. More than 60,000 tickets had been sold by yesterday lunchtime for this transparent money-earner and it is undeniable that the chance to say goodbye has swollen the audience. If you don't like a little wizardy with your grunt and biff then Cardiff is no place for you today.
Rob Howley, the Welsh skills coach, is not prone to the grand statement, but after their run-out at the Millennium Stadium yesterday he was prepared to anoint the 34-year-old with something resembling Godly status. "Those of us who have played with Shane over the last 11 years are fortunate to have played with one of the greatest ever," said the former scrum-half, who went on to label him "a priceless asset".
Howley was there at the beginning, for the sound of pitter-patter feet, if you like. "I remember when he came on against France for his debut – his jersey looked heavier than him," he said. "He isn't 6ft 4in and 17 stone; when he started he was 11 stone. To survive the way he has is incredible. He has scored tries you wouldn't think any player had the right to score and caused havoc in opposing defences for a decade or more. No matter what or who was up against him, Shane always found a way and hopefully he'll find a way again on Saturday afternoon."
Robbie Deans, the Australia coach, admitted he is "concerned" by the Williams effect. Nine years older than the next youngest in the backline, Jamie Roberts, Williams plainly inspires the youngsters. "His ability and professionalism has rubbed off on them and if you want to see Shane's legacy it's right there – in George North and Leigh Halfpenny," said Howley. "He has taken 'back-three' training sessions with them. He understands angles, line-speeds, how defences operate. But he leaves a legacy off the field as well. He's very disciplined."
What's required today will be rather more than their performance in the third-fourth play-off in the World Cup when Australia won rather more cosily than the 21-18 scoreline suggested. "We weren't there emotionally for that game after the semi-final," said Howley. "But we won't have any of the baggage this time. You will see an emotionally charged Welsh team who really want a southern hemisphere scalp.
"We can't allow them to turn over the ball as much as we have in the past. Another thing is the physicality we showed in the World Cup. That starts at the scrum and line-out and we have to ask Australia questions in those areas. But we want to play rugby."
To that end, the roof will be shut, a positive move welcomed by Australia, who were forced into a late change yesterday when a tight hamstring forced the centre Rob Horne to stand down meaning that nine of their regular starting XV are absent. Meanwhile, Wales are missing five of their strongest line-up.
A lot will rest on Sam Warburton's shoulders, as he makes his first Wales appearance since that sending-off and if he and his fellow back-rowers can secure ground control – and if Rhys Priestland can give James O'Connor the lesson he probably still requires in fly-halfery – Warren Gatland's men may reprise their victory of three years ago.
That game was notable for a score in the fifth minute from none other than Shane Williams. That, and many more of 59 international tries, will be recounted this weekend as Shane-mania breaks out across Wales. It is not just the passing of an individual but also of a type of wing which will fuel the emotion. "Shane is the last of a dying breed," said Barry John, a No10 they still call the King. "The likes of Gerald Davies and Shane William, they're gone and it's very, very sad because these guys brought something special. I suppose it's now a modern game of jumbo-jet rugby and juggernauts – I don't think it's that appealing."
Shane's six of the best for Wales
Some of the great tries Williams will be remembered for
1. v Fiji 2007
World Cup heartache for Wales, but Williams provides consolation with a burst down the right wing to leave Fijian after Fijian upended before a dramatic swallow dive under the posts.
2. v New Zealand 2003
The game which "made" Williams, his contribution in valiant defeat was stunning with the highlight a try in the corner which summed up his pace, his awareness and his chutzpah.
3. v Ireland 2008
Williams seals his nation the Triple Crown at Croke Park when going through a gap many still believe simply wasn't there and leaving Andrew Trimble doing a tango with his shadow in the process.
4. v South Africa 2008
No arguments about the World Player of the Year award as Williams humiliates the world champions' defence in their own back yard. Pretends to go inside then outside, leaving the Springboks in mid-hokey-cokey.
5. v Australia 2008
Williams the team-man as he breaks through the line, gives a classic offload to Lee Byrne and is then waiting on his wing when the ball eventually comes his way again. His pick-up was sheer class.
6. v Italy 2005
A Gareth Thomas counter-attack led to what was perhaps Williams's most aesthetically pleasing try. A beautiful move was finished off with a glorious sidestep by Williams as he lit up Rome.