It is a question the All Blacks star is desperate to answer next year.
The dual-code international has never played sevens -- the format of the game making its debut in Rio -- but he is targeting a spot in New Zealand's squad for the 2016 Games.
"Going back in time, the best sportsmen ever have been Olympians -- (Usain) Bolt, (Muhammad) Ali," he told reporters
ahead of the 2015-16 Sevens World Series.
"It's just an awesome opportunity. As a sportsman, most would like to go to the Olympics -- and I haven't achieved that."
Williams made headlines after the Rugby World Cup final in London on October 31, when he gave his winner's medal to a young fan who was tackled by stadium security after he tried to get near his heroes on the pitch at Twickenham.
Tournament organizers promptly gave Williams a replacement medal
, and now his thoughts have turned to learning the finer arts of the seven-a-side game in just a few months.
But adapting to new sports has never phased the 30-year-old.
He began his career in rugby league and represented his country as a forward before switching codes to 15-a-side rugby union and winning World Cups in 2011 and 2015 with the All Blacks
, playing in the backs. In between those triumphs he switched back to league and played for the Kiwis in the 2013 World Cup final.
Throw in a stint as a professional boxer -- he was New Zealand heavyweight champion in 2012 -- and Williams' versatility is clear.
His agility, power and passing game make him perfect material for sevens, with more space to exploit and limited time spent in contact situations.
"I see him adjusting very well to the fast pace of sevens. He'll be a great attacking weapon with his speed, strength and uncanny ability to offload," New Zealand's longtime sevens coach Gordon Tietjens said when unveiling the squad
Williams did not play in the opening event of the World Sevens Series in Dubai, where Fiji beat England in the final -- though he attended and watched his sister Niall make her debut for New Zealand in the women's tournament before heading to Lebanon as part of his charity work.
Williams, who was not picked for this weekend's second round in Cape Town, is expected play in six of the 10 rounds as he bids to win selection for Rio.
Rugby union has featured in the Games four times previously between 1900 and 1924, but its reintroduction in the form of sevens -- often seen as a stepping stone or a fun alternative to the 15-man version -- is proving a big lure.
Williams could be joined in the rush to Rio by All Blacks colleague Liam Messam, former Australia star Quade Cooper and South Africa's record try-scorer Bryan Habana.
Messam, 31, won two Commonwealth Games gold medals in sevens earlier in his career and has also been named in New Zealand's training squad, while the 27-year-old Cooper has recently joined big-spending French side Toulon after lengthy contract wrangles to secure time off to play in the World Series.
Cooper's Toulon teammate Habana, who ended the 2015 World Cup sharing the tournament's overall try record with the late Jonah Lomu, has been named in South Africa's wider 34-man sevens squad along with several Springboks teammates.
Mindful that sevens has become a desirable commodity, national coaches could face a tricky task managing their talent, while players and club chiefs will be checking contracts to check availability.
Great Britain's Olympic rugby coach Simon Amor has even more to juggle.
His 12-man Rio squad will need to comprise the cream of players from England -- which he coaches in the World Series -- Scotland and Wales.
But while New Zealand is the dominant force in the 15-a-side game, and sevens world champion after success in 2013, the reduced format is more open.
The United States, gold medalist in 1924, recorded its historic first victory against New Zealand to finish third in Dubai, while Russia reached the women's final before losing to Australia.
After South Africa, the sevens circuit moves to Wellington, Sydney, Las Vegas, Vancouver, Hong Kong, Singapore, Paris and London for May's finale.