Wales have not beaten Australia Down Under for 43 years, but a three-Test series in Brisbane, Melbourne and Sydney offers a gilt-edged chance to build on this season's successes.
The World Cup semi-finalists and reigning RBS 6 Nations Grand Slam champions are geared towards taking what they see as the next step.
Victories over the southern-hemisphere heavyweights have frustratingly and repeatedly eluded them.
Wales' singular wins against New Zealand and South Africa both came in Cardiff, while not since 1969 - and a 19-16 triumph at Sydney Cricket Ground when Gerald Davies, John Taylor and Dai Morris scored tries - have they prevailed Down Under.
But Williams, who bowed out of Test rugby in Barbarians colours during their 30-21 loss to Wales yesterday, believes his former team-mates can make their presence felt this month.
"It's going to be tough," he said. "It is a big ask to win the series against Australia - one of the best sides in the world - on their home turf, but I think that is where we need to get to now.
"We've won the Grand Slam and we need keep going on an upward curve.
"I do see Wales winning a Test out there - whether or not they win the series I don't know - but they have certainly got a good enough squad."
An advance party of 16 players, including many Grand Slam winners, are already in Australia preparing for the Brisbane opener next Saturday under assistant coach Shaun Edwards' direction.
Caretaker tour boss Rob Howley and an 18-strong playing group are set to join them in the next 48 hours, and among that second tranche will be 19-year-old Cardiff Blues wing Harry Robinson.
Robinson and 20-point centre James Hook proved the shining lights of a disjointed Wales display against the Baa-baas - and Williams was suitably impressed.
He could only watch as Robinson scored a superb 60-metre try, while his appetite for work throughout the contest served notice that Wales wing play is not just all about giants George North and Alex Cuthbert.
"Harry had a fantastic game. He scored a try early on, and I was chuffed for him," Williams said.
"He worked hard throughout the game, and for a young guy he didn't show that he was intimidated whatsoever. He took his chance well.
"I told him after the game I was chuffed to bits for him. He has come into a Grand Slam-winning squad and he was under a lot of pressure, so for him to go out and play like he did shows he has got a mature head on him.
"He made a big impact. He made some great breaks. He was all over the park, and that is what you want.
"I hope he gets lots more chances, and I am sure he will after his performance.
"And James is that versatile - it is a coach's dream. He caused us problems all day, and he looked to have a spring in his step.
"He is enjoying himself in France with Perpignan, and he's playing with a lot of confidence.
"He is one of the best players I have played alongside - it is good to see him back to his best."
There will be no more rugby for Williams, though, after the 35-year-old record Wales try-scorer bid farewell in front of a 57,000 Millennium Stadium crowd.
He could not repeat the feat of scoring tries in his final games for Wales, the British and Irish Lions and the Ospreys, but there were still flashes of brilliance that proved his trademark during a memorable 12-year Test career.
"That was my final game, and what a great place to have had it," said Williams, whose long-time Wales colleague Martyn Williams also retired after winning his 100th cap to join fellow Welsh centurions Stephen Jones and Gareth Thomas.
"It was a fantastic occasion, and I've had a great time. The Millennium Stadium was where it all started for me - and where it has all ended," Shane Williams added.
"It was very strange playing against Wales, but it was no holds barred on the pitch. The boys are competitive - that's why they play rugby - and everyone is out there to win.
"But I went over and had a chat after the game and wished them all the best for the tour."
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