He didn't represent them at Craven Week level though and opted to move to Pretoria to join the Blue Bulls academy after high school.
He started their 48–13 victory over Free State U19 in the semi-final,[4] as well as the final, where the team suffered a 19–20 defeat to the Golden Lions U19s in Johannesburg.
[8] He started his third match of the tournament as South Africa easily dispatched Argentina in the semi-final, winning 35–3,[9] and was named on the bench for the final against New Zealand.
Adendorff scored his third try of the campaign in a 50–24 victory over the Free State U21s in the semi-finals,[15] but again suffered defeat in a final, with his side losing 18–22 to Western Province U21 to finish as the competition's runner-up.
UP Tuks beat UJ 61–24 in the semi-final[20] and three-time champions Maties 44–5 in the final[21] to win the competition for the second consecutive season.
He made his first class debut in a 110–0 victory over the Limpopo Blue Bulls in Lephalale[22] and also appeared in matches against the Griffons[23] and the Eastern Province Kings.
Following a victory over the Sharks in the semi-final,[27] Adendorff ended on the losing side of a Provincial Championship final for the third consecutive season as the Western Province U21s beat them 30–23 in Cape Town.