He was recruited by the Brisbane Lions with the 39th selection in the 2015 national draft. He played his first senior game in round 9 of the 2016 season against Melbourne. In his time at the Lions he has been known for his on-field antics, in particular his goal celebrations. Upon kicking his first AFL goal, Rhys celebrated with a 'shotgun' move made famous by Hawthorn'sMark Williams and faced some criticism for this showboating, while the Lions were losing to Greater Western Sydney in round 17, 2016.[5]
After his delisting, Mathieson joined Brisbane-based QAFL side Wilston Grange. Mathieson also took up Bodybuilding, and took on a heavy supplement program to build muscle. Mathieson's body transformation led to suspicion from anti-doping authorities, and Mathieson was target-tested at the local sporting level. Mathieson tested positive for Oxymetholone and was suspended from football for 3 years, despite no longer playing professionally.[6] Mathieson admitted he was more worried about his new bodybuilding hobby, and knew the risk he was taking with regards to his local footy career.[7]
↑The 2020 season was played with 17 home-and-away matches per team (down from 22) and 16-minute quarters with time on (down from 20-minute quarters with time on) due to the impact of the COVID-19 pandemic.
