He played for the in youth competitions and was part of the 2009 Vodacom Cup squad, without making a senior appearance. He then moved to Potchefstroom in 2010, where he played four matches for the in the 2010 Varsity Cup competition. He also played for the team during the 2010 Under-21 competition.
Leopards
Although he didn't play any games for the during the 2010 Currie Cup season, he made his first class debut in the Leopards' first relegation play-off match against the, scoring his first try within a minute of his debut when he came on as a first-half blood replacement and a second try right before the end of the match. He maintained his try-scoring exploits in the following match, scoring another try in the return leg to help keep the in the 2011 Currie Cup Premier Division.
Kings
It was then announced that he moved to the for the 2011 Currie Cup First Division season. He remained with them for three seasons, making 36 appearances for them in the Currie Cup and Vodacom Cup competitions in 2011 and 2012. He reached the top ten in the scoring charts for the 2011 Currie Cup First Division, scoring ten tries and two conversions during the season. He firmly established himself as the first choice full-back, starting fifteen of their sixteen matches in the 2012 Currie Cup First Division season and also started their match in the First Division final, which the Kings won 26–25 to win their second First Division title in three seasons. In 2013, he was also named in the squad for the 2013 Super Rugby season. He made his Super Rugby debut for the Kings in their first ever Super Rugby match, a 22–10 victory over Australian side the in Port Elizabeth. After starting the first three matches of the season, he missed the next seven due to a knee injury. He returned to make a further five appearances, as well as playing in both legs of the Kings' Super Rugby promotion/relegation play-offs against the, which saw the Kings lose their Super Rugby status.
Sharks
He joined the exodus of players leaving the Kings after their defeat to the, joining Durban-based side the for the 2013 Currie Cup Premier Division season. He made his debut in their second match of the season against the and immediately established himself as their first-choice full-back, starting all the remaining games of the season, scoring four tries. He was also in the starting fifteen for the Currie Cup final, which the Sharks won 33–19 against. He was included in the squad for the 2014 Super Rugby season and made his Sharks Super Rugby debut in a 31–16 victory against the in Durban.
Return to Kings
At the end of 2015, Marais was one of a number of players that joined the Southern Kingsprior to their return to Super Rugby for the 2016 season. However, the – the provincial union that was supposed to administer the Super Rugby team – suffered serious financial problems and the South African Rugby Union stepped in to assist the Super Rugby franchise; however, Marais was not one of the players contracted by SARU to represent the Southern Kings. After being unpaid for several months, he was one of eighteen players involved in submitting an application to get Eastern Province Rugby liquidated in an attempt to recoup unpaid salary payments.
Bulls
Shortly after the 2016 Super Rugby season kicked off, Marais joined the Pretoria-based on a two-month trial basis. He made his Bulls debut by replacingBurger Odendaal during their 23–18 win against the in Round Six. He was named in their starting line-up for their next match, against Marais' former side the in Port Elizabeth.
