One-Test All Black James Broadhurst announced his retirement from rugby on Friday, saying he had been unable to shake off the impacts of concussion.
The 29-year-old has not played since suffering two head knocks representing Taranaki in August 2015, revealing he still suffers symptoms that affect his daily life more than 18 months later.
Broadhurst said it was difficult to walk away from the game he loved but was following medical advice to put his health first.
"For a door to open, others must close, so I look forward to the next chapter in anticipation, rather than looking back at the rugby chapter with sadness," he said in a statement released by his Wellington Hurricanes Super Rugby club.
The towering lock helped the Hurricanes to the 2015 Super Rugby final and was being groomed for a role in New Zealand's World Cup squad.
All Blacks coach Steve Hansen had handed him his international debut -- a 27-20 win over the Springboks at Ellis Park -- just weeks before he received the fateful blows to his head.
The Hurricanes said Broadhurst had made considerable progress in his recovery but it had now "plateaued".
New Zealand Rugby general manager Neil Sorensen commended Broadhurst's decision and urged other players facing a similar dilemma to follow his example.
"James has put his health first and that is the right call," he said.
High-impact sports such as rugby are struggling to deal with concussion -- which occurs when a blow to the head or body makes the brain bounce or twist in the skull.
An "invisible injury" that is sometimes dismissed as a badge of honour in macho sporting cultures, it does not always result in loss of consciousness and often does not show up on brain scans.
But researchers, including some working with rugby union players, have pointed to possible links between multiple concussions and long-term brain damage.
As a result, sideline concussion protocols have been tightened and some unions are trialling "blue cards", which a referee can use to send a concussed player off the field for mandatory treatment.