Wales defence coach Shaun Edwards admits he is not surprised Sam Warburton has decided to retire from rugby union at the age of 29.
Cardiff Blues flanker Warburton, who also successfully captained Wales and the British & Irish Lions, returned to training this summer following neck and knee surgery but announced on Wednesday he was calling time on his playing career.
"I can't say I am surprised. To be out of this, an unbelievably physical game, for that amount of time, and then to come back, is understandably difficult," said Edwards.
"He has realised his body can't take it anymore and I think he has made a good decision as he is going out on his own terms.
"It's an unbelievably difficult game to play and only when you've been out there at the very highest levels do you know what fitness levels [are required], how much pain you have to go through and what difficulties you have to deal with.
"Only then can you understand why Sam Warburton has made his decision."
Warburton's last game came playing for the British and Irish Lions in the dramatic 15-15 draw with New Zealand in July 2017, a result that saw Warren Gatland's touring side secure a hard-fought 1-1 series draw.
It was only a late intervention from Warburton in that match that saw French referee Romain Poite change his mind after initially blowing for an offside penalty, a decision that denied the All Blacks a comfortable-looking penalty to secure victory.
Edwards believes Poite only did so because of Warburton's reputation and paid tribute to him.
"Sam Warburton will be remembered as a gentleman off the pitch and an unbelievable competitor on the pitch," added Edwards.
"I think his last act in rugby was probably one of his greatest, which was to get the referee to change his mind in that great Lions series.
"Thankfully, for all Lions fans, he did manage to change his mind. Only through his previous behaviour would have changed his mind and it was a memorable thing to finish his career with."