Australia captain Boyd Cordner has retired from rugby league because of the concussion symptoms that have kept him on the sidelines since last November.
Cordner, who turned 29, announced his decision to retire on Monday, days after abandoning his latest plan to return to the National Rugby League for an 11th season with the Sydney Roosters.
Cordner's decision comes a little over two months after his Roosters team-mate and fellow co-captain Jake Friend cited head injuries as his reason for quitting the sport.
The NRL has launched a severe crackdown on high tackles this season, resulting in record numbers of players being cautioned, sent off or suspended. Cordner backed the clampdown.
"Player welfare and player safety has got to be the forefront of everything," he said.
"There has been a lot of talk about the way the games changed, and it is changing, but in all of that we have got to find a really good balance with it.
"We are starting to find that."
The star forward has undergone rigorous testing since being knocked out in the opening game of the 2020 State of Origin series and was recovering well, but he decided it was time to retire after sensing concern among his family about returning to the NRL.
"The last six months or so have been a really challenging time in my life," said Cordner.
"All I ever wanted to do was get back and play the game that I love and most importantly for the club I love.
"I am at a stage now where I am doing really well. I'm fine, I'm back at training with the team and I was getting ready and prepared to play.
"But, deep down I knew I wasn't 100 per cent fully recovered. The feeling of going out (and playing) and what the next head knock looked like to me, I couldn't get that out of my head."
Cordner featured 20 times for Australia, captaining the Kangaroos since 2018, and scored the only try of the Rugby League World Cup final in 2017 when Australia defeated England.
The second rower won two World Cups and three NRL Premierships with the Roosters in 2013, 2018 and 2019.
He also led New South Wales to State of Origin series wins in 2018 and 2019 after a prolonged period of Queensland dominance.
"Boyd is one of the greatest leaders of men I have seen," said Roosters coach Trent Robinson.
"At any level of the game, I'm sure that every player who ever stood alongside Boyd would thank him for being the team-mate and leader that he was."