In 2014, he was selected to represent the Limpopo Blue Bulls at the premier high school rugby union competition in South Africa, the Under-18 Craven Week.
[6] Janse van Rensburg represented the NWU Pukke in the 2016 Varsity Cup, where he made history in their opening match against the UP Tuks; the Varsity Cup adopted a points system whereby tries that originate within a team's own half were worth nine points, and Janse van Rensburg scored the first nine-point try in the competition after just nine minutes.
[16] After another start against the SWD Eagles,[17] he dropped to the bench for their match against the Boland Cavaliers, but came on to score his first points in first class rugby, converting two late tries.
He was included in their squad for the 2016 Currie Cup Premier Division,[21] but didn't feature for the team, instead making two appearances for the Sharks U21 in the 2016 Under-21 Provincial Championship.
[23] Following the collapse of London Irish into administration, Janse van Rensburg was signed by English Premiership side Bristol Bears.