He was then one of two South African youngsters that moved to Australia to join rugby league side the Sydney Roosters, the other being Brian Skosana. He never played for the first team, but did represent their Under-20 side in the 2010 Toyota Cup.
Rugby union
Melbourne Rebels
In 2010, Du Plessis reverted to rugby union, signing with the Super Rugby side for their inaugural season in Super Rugby in 2011. He made a single Super Rugby appearance for the Rebels, coming on as a late replacement in their match against the.
Du Plessis returned to South Africa in 2011 to sign for the Cape Town-based. He made seven appearances for the side during the 2011 Under-21 Provincial Championship, scoring five tries which included four in their 38–42 loss to the s in Johannesburg. He was included in the ' 2012 Super Rugby squad. He made two appearances for them off the bench, a 23–13 victory over the in Brisbane and a 17–3 victory over the in Perth a week later. He also made seven appearances for Western Province in the 2012 Vodacom Cup and scored a try against the. Still eligible for play at Under-21 level, he played for the side during the 2012 Under-21 Provincial Championship and scored one try in their match against the. He was then called up to their Currie Cup side and made nine appearances for them during the 2012 Currie Cup Premier Division. He scored tries in their matches against and the to help them finish in third spot on the log to qualify for the semi-finals. However, he didn't feature in the semi-final or the final instead reverting to the Under-21 side; he played in both their 19–18 semi-final victory over the and their 13–22 defeat by the in the final.
Montpellier
He didn't feature for the Stormers in the 2013 Super Rugby season and opted to move to France to join Top 14 side prior to the 2013–14 Top 14 season. However, he failed to break into the first team at Montpellier due to suffering a knee injury and featured in just one match for them, coming on as a late replacement in a 25–18 victory over.
He returned from France after just one season to join the prior to the 2014 Currie Cup Premier Division. He made five starts and five appearances off the bench for the Bloemfontein-based side, scoring a try in their match against the as the Free State Cheetahs finished in fifth spot to miss out on the play-offs. He wasn't named in the Super Rugby squad for the 2015 Super Rugby season, instead playing in four matches for the side that played in the 2015 Vodacom Cup competition.