But the former Canberra mechanic has swapped her hockey stick for footy boots and the chance to create history in Rio as the Australian rugby sevens skipper.

Williams will join the 410-strong Australian team as they start start chasing Olympic medals in Brazil when the Games begin on Saturday morning and her team is a gold-medal favourite.

She's also part of a group of 20 current and former Canberra athletes who get a chance to achieve their dreams.

Here are the top five Canberra medal prospects on the eve of the opening ceremony.

SHARNI WILLIAMS – rugby sevens

Williams moved to Canberra as a budding hockey star who went to watch her friends play for Royals in the capital's women's rugby union competition.

After some coaxing, she finally took the leap on to the field and since then she's led the sevens team to world title glory.

The Australian side is regarded as the team to beat in Rio after dominating the world series and Williams made her comeback from a knee injury in time to take her place as captain.

"I've been dreaming of this since I was eight years old," Williams said.

"I definitely wanted my Olympics dream to be hockey, but rugby ended up being my choice and rugby has been my pathway for eight years now.

"I've never looked back and this moment is exactly why I haven't looked back. It's indescribable."

Canberra schoolboy rivals Tom Cusack and Lewis Holland will play in the Australian men's team.

CAROLINE BUCHANAN – BMX

BMX queen Buchanan left the London Olympics in tears as her gold medal hopes crumbled in the final four years ago.

But the 25-year-old will race in Rio with a steely determination to make amends for her Olympic heartbreak.

Buchanan has been based overseas for the past six months to give herself the best possible chance of winning a medal.

Buchanan won the world championship time trial event and finished runner-up in the world championship race earlier this year to send a warning to her rivals.

Since her disappointment in London, Buchanan has won two BMX world titles and a mountain bike world title.

Defending Olympic champion Mariana Pajon looms as her biggest hurdle. The harsh reality of BMX is that one bad turn or poor positioning can shatter a dream.

ANDREW CHARTER AND GLENN TURNER – hockey

A two-metre high fence separated Andrew Charter from the Olympics in London, but the Kookaburras goalkeeper has a chance to help the team win its first gold medal since 2004.

The Kookaburras are the No.1 ranked team in the world, but they're driven by having to settle for bronze at the past two Olympics.

Charter was the first reserve for the team in London and had to stay outside the athletes' village because he wasn't a fully-fledged member of the team.

Now he's a part of the best team in the world and has a chance to put his demons to bed by scoring an Olympic medal.

"It's pretty exciting but relief as well. It's pretty polarising to the way I was feeling four years ago. In 2012 I was pretty upset and disappointed," Charter said.

"This year it's relief and joy that the last five years of my career have come to this and hopefully we can put a good performance on."

Turner almost retired when injuries threatened to ruin his hopes of making it to Rio. But the Goulburn council worker wasn't prepared to give up on the chance to win gold.

PATTY MILLS – basketball

The Rio Olympics looms as the Australian Boomers' best chance to win their first medal and Patrick Mills will be the key man to ignite their hopes.

The Boomers boast four NBA championship winners and Mills is playing at his third Olympics despite being just 27 years old.

The Boomers will have chances in the future when NBA No.1 draft pick Ben Simmons and Dante Exum are available for international duties.

But Andrew Bogut is nearing the end of his international career and Mills is in his prime after helping the San Antonio Spurs to an NBA title two years ago.

Mills was the highest point scorer of all teams at the 2012 Olympics, including a star-studded United States squad that was led by Lebron James, Kobe Bryant and Kevin Durant.

"We know what it takes to achieve something we haven't done before," Mills said.

"We established this goal for us a long time ago and it's a high goal but we all believe in it.

"If you don't believe there is no point in being here. We have a really tight-knit group that believes in us and [wants] to try and accomplish something we've never done before."

KIM BRENNAN – rowing

The Canberra lawyer has a chance to become Australia's golden girl of Rio if she can break through for her maiden moment of glory.

Brennan (nee Crow) won silver and bronze in London four years ago, but has since built up an imposing record to be unbeaten in her single sculls event since 2014.

She won the world championship race last year and the 30-year-old has her eyes firmly set on a golden prize in Rio.

Brennan is considered the Australian team's best chance of winning individual gold but will face stiff competition from New Zealander Emma Twigg.

Redemption time: Jared Tallent

The former Canberra walker is desperate to get his golden Olympic moment after his previous bids were thwarted by drug cheats. Tallent was awarded a retrospective gold medal in June after the man who beat him in London, Sergey Kirdyapkin, was stripped of his medal for doping.

High hopes: Nathan Hart

Team sprint cyclist Nathan Hart has cemented his place as the lead rider and he will be intent on winning a medal after missing out at the world championships by the smallest of margins. Hart will team up with Pat Constable and Matt Glaetzer as they aim to improve on their fifth place at the world championships.

Swansong: Alicia Coutts

Coutts is the sometimes forgotten star of the Australian swim team, but she deserves to go out on a high in Rio as she prepares for retirement. Coutts stood tall when the swim team imploded four years ago, winning five medals in an outstanding effort. Rio will be her third and final Olympics.

RIO-BOUND CANBERRA ATHLETES

Athletics: Melissa Breen (100 metres), Zoe Buckman (1500 metres), Chris Erickson (50 kilometre walk), Tanya Holliday (20 kilometre walk), Brendon Reading (50 kilometre walk), Kelsey-Lee Roberts (javelin), Brett Robinson (5000 metres), Rachel Tallent (20 kilometre walk), Jared Tallent (20 kilometre walk and 50 kilometre walk), Lauren Wells (400 metre hurdles).

Basketball: Patrick Mills, Marianna Tolo, Stephanie Talbot.

Boxing: Shelley Watts.

Cycling: Nathan Hart (team sprint), Gracie Elvin (road), Caroline Buchanan (BMX), Rebecca Henderson (mountain bike), Daniel McConnell (mountain bike).

Soccer: Michelle Heyman, Lydia Williams.

Hockey: Edwina Bone, Emily Smith, Andrew Charter, Glenn Turner.

Rowing: Kim Brennan (single scull).

Rugby sevens: Sharni Williams, Tom Cusack, Lewis Holland.

Swimming: Alicia Coutts (200 metre individual medley), Matt Abood (50 metres freestyle, 4x100 metre freestyle relay).