St Helens half-back Lance Hohaia has been forced to retire from rugby league after suffering from "post-match concussion-type symptoms" since returning from being knocked out by Wigan prop Ben Flower in last year's Grand Final.
The 32-year-old played just two minutes of the Old Trafford showcase before being punched twice by Flower following an altercation with the Welsh international, who was banned for a record six months for the offence.
After serving a one-game ban for a forearm on Flower in the lead up to the incident, Hohaia has made eight appearances for Saints this season but his career has been curtailed as he continues to be troubled by the episode.
"I have been experiencing recurrent post-match concussion-type symptoms since returning to play," he told the BBC.
"I am currently seeking expert medical advice to understand any potential effects to my long-term health.
"However, in the meantime I would like to say that I am extremely grateful for the career I have had and the opportunity to play for my country and such prestigious clubs as St Helens and the NZ Warriors.
"I would also like to sincerely thank all those who have supported me throughout my career and during this difficult time."
The New Zealand World Cup winner joined St Helens in 2012 and has made 80 appearances for Keiron Cunningham's side, scoring 22 tries.
A club statement read: "Lance has been a valued and integral member of the squad for the last three and a half years and we thank him for his service.
"We wish him and his family well in their life after rugby league with St Helens. St Helens will make no further comment on this matter."