Knights hooker Rory Kostjasyn has announced his retirement from the game due to complications arising from a throat injury sustained during pre-season training.
After winning the 2015 Telstra Premiership and 2016 World Club Challenge with the Cowboys Kostjasyn was signed to add experience to the Newcastle spine and help nurture the club's next wave of young dummy-halves.
However the injury sustained prior to the start of the 2017 season meant he was never able to take to the field with the Knights.
"Retirement was a combination of medical advice and how my body was unable to adapt to a reduced airway," Kostjasyn said via a club statement.
"It has by far been the most challenging six to seven months I've faced, not only in my career but in everyday life.
"Unfortunately, it's a challenge that I've been unable to overcome."
Kostjasyn started his NRL career with the Storm in 2010, making 32 appearances across three seasons before moving north to the Cowboys and featuring in 94 games, including the club's maiden grand final win.
The former Ireland international will now move into a coaching role with the Knights, working with the club's most promising young players as an elite pathway development coach.