Marais played club rugby in the Blue Bulls' Carlton League, where he played for Adelaar and for Naka Bulls. He played for and captained Naka Bulls from their formation in 1998 until 2003, when he took over as assistant coach to Cassie Prinsloo. In 2005, Marais was also appointed as the head coach of Hoërskool Overkruin, guiding them to the Beeld Trophy for medium-sized schools in his first season in charge. He worked as a senior logistics planner, but quit this role in 2007 to take up coaching on a full-time basis. In 2010, Marais was appointed as the coach of university side. He won the Carlton League with them to help them qualify for the National Club Championship. He guided UP Tuks all the way to the final of the 2011 Varsity Cup, where they lost 16–26 to the. Shortly after the 2011 Varsity Cup season, Marais took up a coaching role with the, taking over as head coach of the side. Under his tutelage, the side won the 2011 Under-21 Provincial Championship, beating the s 46–30 in the final. He remained as the coach for the 2012 Varsity Cup and helped them win the competition for the first time, beating three-time winners by winning 29–21 in the final. He once again guided the side to the 2012 Under-21 Provincial Championshiptitle after they beat 22–13 in the final. He helped retain the Varsity Cup in 2013, this time beating Maties comprehensively in the final, running out 44–5 winners. That was Marais' final Varsity Cup campaign in charge of UP Tuks, with former coach Pote Human taking over as their new coach for the 2014 Varsity Cup. Marais took charge of the ' Vodacom Cup team and took them to the Quarter Finals in the 2013 competition, where they lost to the. Marais led the Blue Bulls U21s to their third consecutive final in the 2013 Under-21 Provincial Championship, but fell short on this occasion, losing 23–30 in the final to Western ProvinceU21. His Blue Bulls side reached the semi-final of the 2014 Vodacom Cup tournament, where they lost 15–16 to trans-Jukskei rivals, the. He won the Under-21 Provincial Championship for the third time in four years in 2014, beating Western Province U21 20–10 in the final in Cape Town. He guided Blue Bulls to their third consecutive quarter final appearance in the 2015 Vodacom Cup, this time reaching the semi-final where they lost 6–10 to. Following the departure of head coach Frans Ludeke in June 2015, Marais was appointed as the head coach of the Blue Bulls' 2015 Currie Cup Premier Division campaign. Shortly before the end of the 2015 Currie Cup campaign, it was announced that Marais would also take over as the head coach of the prior to the 2016 Super Rugby season, signing a four-year contract.
