Bristol centre Will Hurrell retired on Friday after suffering a probable stroke following an English Premiership match earlier this season.
Hurrell was taken ill after the match against Leicester at Welford Road on 4 January.
The 30-year-old came off with a head injury during the second half and was treated at Leicester Royal Infirmary.
Following medical advice, Hurrell has now decided to hang up his boots.
"After speaking with specialists, I've been advised that I can't engage in any contact sports because of my head injury," said Hurrell, who made 68 appearances during his four seasons with Bristol.
"It's been a really challenging year for me personally, but I accept this is the right decision for me and my family.
"I've been lucky to have played the sport I love and to have met brilliant people along the way. I'm proud of the career I've had and to have represented some fantastic clubs."
Bristol director of Rugby Pat Lam added: "Will is a popular team man at the club and we're sad to see his career cut short by injury.
"It was a pleasure to work with him and to have him as a friend."