Despite not representing at secondary school level while a scholar at Paarl Boys' High School, Marais were included in the squad for the 2007 Under-19 Provincial Championship after he moved to Bloemfontein to enroll at the University of the Free State. He also represented his university side in the Varsity Cup competition, playing for them in five consecutive seasons between 2009 and 2013, amassing 26 appearances and scoring three tries.
His first class debut came during the 2010 Vodacom Cup competition. He missed the early rounds of the competition due to his involvement in the 2010 Varsity Cup competition, but made his debut by starting in their Round 6 loss against Argentinean invitational side the in Parow, Cape Town. He remained in the starting line-up for the remainder of the competition and helped the Free State XV reach the final, where they lost 31–29 to the. He remained involved in the Free State's Vodacom Cup campaigns in 2011, 2012 and 2013, making a total of fifteen appearances. However, he was never included in a Currie Cup squad during his time in Bloemfontein.
Griffons
His lack of involvement in Currie Cup action for the saw Marais have two short spells at near-neighbours the. He made his Currie Cup debut for them during the 2012 Currie Cup First Division in their match against the, marking the occasion by scoring his first ever senior try early in the second half. He made five appearances in the competition for the Welkom-based side and returned for one match in 2013, coming on as a substitute against the in Nelspruit.
Marais moved to Johannesburg to join the for the 2014 season. He was a regular in their squad for the 2014 Vodacom Cup competition, playing in all ten of their matches during the competition, starting eight of those. He was once again involved in a Vodacom Cup final, but once again ended up on the losing side, as the Golden Lions lost 30–6 to in Kimberley. Marais also made his Super Rugby debut during the 2014 season, coming on as a substitute in their match against the after being a late inclusion on the bench following Julian Redelinghuys' withdrawal through injury.
In July 2014, it was announced that Marais would join the prior to the 2014 Currie Cup Premier Division competition. He signed a deal that would see him play for the Port Elizabeth-based side until the end of 2016.
