Wales and Scarlets back Morgan Stoddart has retired with immediate effect after failing to recover from a broken leg.
The 28-year-old was six games into his Scarlets comeback after 14 months out with a double leg fracture.
But he has experienced "significant pain" since his return and has followed medical advice to stop playing.
"It's not easy to give up your rugby career but when it really is impossible to carry on you just have to accept it and get on with it," he said.
Stoddart broke his left leg while winning his eighth cap for Wales in a pre-World Cup game against England at Twickenham in August 2011.
23 September 1984, Pontypridd
Scarlets, Llanelli Pontypridd, Treorchy
Eight caps for Wales, scoring five tries
The versatile back, who played primarily at full-back, was not expected to start the match, but an injury to fly-half Stephen Jones during the warm up forced a late reshuffle.
He sustained the injury early in the second half when he was tackled by Delon Armitage, having intercepted a pass from the England player.
Scarlets eased him back into action with a second-half appearance as a replacement against Newport Gwent Dragons on 5 October.
He showed no ill-effects of the injury, making a real impact in the final stages and scored the final try in a 23-14 victory at Parc y Scarlets.
But problems gradually resurfaced in the next games and he was forced off early against Munster on 25 November in what will now prove to be his final appearance.
"I worked as hard as possible in the year I was off to get back on the pitch and that can be a difficult period for any injured player mentally, as well as physically, but I was determined to get back to playing," added Stoddart, who scored a try on his Wales debut against South Africa in 2007.
"But ever since I've been back on the field I've had significant pain in the leg throughout and that has not improved.
"Following a series of medical tests and consultations, detailed scans and strength tests, I've been advised that I cannot continue."