[1] Guyton spent the previous three years playing for North Otago in the Heartland championship, making 29 appearances for the province.
[2] After another season of little action as a member of the Crusaders, Guyton signed a contract with the Blues,[3] his 3rd super rugby team in as many years.
Guyton announced his retirement from playing rugby in October 2018, aged 28, after repeated concussions suffered in official matches had left him with symptoms of chronic traumatic encephalopathy (CTE).
[6][8] Guyton's family decided to donate his brain to the Neurological Foundation Human Brain Bank at the University of Auckland;[6][8] following post-mortem analyses conducted in New Zealand and Australia, he was diagnosed with stage 2 CTE in March 2024, becoming the first New Zealand-based player to be officially diagnosed with the disease.
[6][8] The pathologist's report also found that Guyton's brain presented trauma-induced cavum septum pellucidum, as well as age-related tau deposits.