Prior to 2017, Segner was playing for SC 1880 Frankfurt, one of the most traditional clubs in Germany's domestic Rugby-Bundesliga competition. He quickly established himself as one of the leading figures in the youth setup of the club and went on to win numerous German youth championships. He also captained his team, while being one of the youngest members. Segner played for Germany Under 16 national squad in 2016. He didn't play for the U18 team though, as he continued his stay in New Zealand.[2]
New Zealand
Segner was on a six month stay in New Zealand in 2017 as an exchange student when he was offered a scholarship by Nelson College, he was then picked for the Nelson College top side.[3][4] Segner then went on to captain the Nelson College top side and led them to their first UC Championship title in twelve years in 2019.[5] In 2018 Segner made the Crusaders Under 18 squad and made his debut for the New Zealand national schoolboy rugby union team against Tonga.[6] In 2021, he was named captain of the Crusaders under 20 side for the Super Rugby Aotearoa Under 20 competition.[7]
Professional rugby
At just 19 years of age, Segner was named in the Tasman Mako squad for the 2020 Mitre 10 Cup,[8] signing a two year deal with the side.[9] He made his debut for the Mako in Round 7 against Southland in a 47-10 win for the side at Trafalgar Park.[10] Segner became the first German to win a Mitre 10 Cup title when Tasman won the 2020 Mitre 10 Cup, beating Auckland 12-13 in the final at Eden Park, with Segner coming off the bench in the second half. Segner had a stand out season during the 2021 Bunnings NPC as the Mako made the premiership final before losing 23–20 to Waikato. In October 2021 Segner signed with Super Rugby side the Blues on a three year deal.[11] He made his debut for the side in Round 2 of the 2022 Super Rugby Pacific season against the Hurricanes.