Born in Cape Town, South Africa, Warner began playing rugby at the age of seven after being introduced to the sport by his father. He developed through Tygerberg High School and represented Western Province at youth level before progressing into the Blue Bulls system. He continued his development at the University of Pretoria, competing in the Varsity Cup.
He built his professional career in South Africa with the Bulls and Lions, competing in Currie Cup, Super Rugby, and URC competitions. He also gained international experience playing in France, further developing his game as a scrum half.
He joined Major League Rugby with the Houston SaberCats in 2024 and made an immediate impact, earning All-MLR First XV honors in his debut season. He later joined the Seattle Seawolves for the 2026 season, bringing experience and leadership to the squad.
Warner credits his early development to his family and coaches and continues to build on that foundation at the professional level. Outside of rugby, he enjoys playing golf.