Former Scotland captain Mike Blair has retired immediately from playing with Glasgow Warriors, a bout of concussion playing a part in his decision.
But the 35-year-old insists that the injury was not the only factor in ending his career.
"It was part of the decision but not the only part," he said. "My age, opportunity to coach, young family."
Blair has yet to fully recover from a concussion suffered in January and will consult a specialist neurology team.
Capped 85 times by Scotland and selected for the British and Irish Lions tour of South Africa in 2009, Blair will now use that experience as an assistant coach with the Scotstoun club next season.
He made 12 appearances for Gregor Townsend's reigning Pro12 champions and was voted player of the month in October, but says time has run out for him to be fit again before the end of the season.
"I actually planned to retire last season, but Gregor Townsend persuaded me to join Glasgow," said Blair, who would have ended his playing career this summer even if he had not been presently sidelined.
"It's a difficult day, but the amount of time I've had in the game I knew it would have to end."
Blair started his professional career with Edinburgh in 2001 and had spells with Brive in France and Newcastle Falcons in England's top flight before joining Glasgow last summer.
"I guess I've been fairly fortunate and it's something I've never really thought about," he said. "I just love playing rugby.
"Being captain of Scotland was a really big thing for me, being involved with a Lions tour and playing in the semi-final of the European Cup with Edinburgh in 2009 will all live long in the memory."
Despite suggesting that he never planned for his long career, Blair said he always had an intensity to win, both in and outside rugby.
"For me, it was always about individual battles," he said. "It was a team game and you did everything to help the team win, but for me if you've got a one-on-one tackle or you're trying to beat somebody, that contest is something that I loved.
"I hate being beaten one-on-one. I remember playing a game of table tennis when my wee brother beat me when I was 14. He was nine. I hated losing those battles."
That determination to win will now be seen from the touchline as Blair prepares to move into full-time coaching at Glasgow next season, but he realises that his experience as a player is no guarantee of success in the new role.
"I don't know if I'm going to make a great coach," he said. "Just because I've played rugby at a high level doesn't mean I will pass that on.
"But I've been working with scrum-halves Henry Pyrgos and Ali Price and really enjoying it.
"Next year is a great opportunity to work with an incredible group of players and management group and I just want to learn as much as I can."
Blair admits he will miss being a player.
"I don't feel it yet," he said. "I feel like an injured player who's not been playing.
"Maybe in six months or a year's time I will. One of the hardest things I've had to do is tell my kids."
Townsend praised Blair for a significant contribution during his short spell at Scotstoun.
"He exceeded our expectations on the field with some outstanding performances and would have been in the running for player of the season before picking up his recent injury," said the Glasgow coach.
"In my opinion, he is one of Scotland's best-ever rugby players and it was great to see him play in a Warriors jersey this season.
"It's disappointing that he's not able to finish his career on his own terms, but he can reflect on a brilliant career both at club and at international level.
"Mike's influence off the field has already had an impact at the club, as our three scrum-halves, Ali Price, Grayson Hart and Henry Pyrgos, are all playing well and that is partly down to Mike's coaching and guidance."