Former Wales international Andries Pretorius has been forced to retire at the age of 29 after being diagnosed with a rare autoimmune disorder.
Pretorius joined Worcester Warriors from Cardiff Blues last year, but never made an appearance for the Championship promotion-hopefuls after suffering chronic injuries in pre-season.
After what the club described as "multiple, inexplicable calf tears", Pretorius started to suffer similar injuries elsewhere on his body.
That prompted Worcester to send Pretorius to a nerve conduction specialist and a neurologist, and the back-row forward was subsequently diagnosed with neuromyotnia, or Isaacs' Syndrome, which cause muscles to continuously cramp and prevents recovery after exercise.
Various different treatments were found to be ineffective, and the rarity of the condition means Pretorius has been left with no other choice but to cut short his career.
"It is with great sadness that I have to announce my retirement from rugby," said Pretorius, who has two caps for Wales.
"Unfortunately, due to the disorder I can't perform to the standard I know is required to push myself and my team-mates without hurting myself.
"I must thank Worcester Warriors, and their medical department in particular, for the endless amount of support they have provided over the last five months.
"No-one had dealt with something like this before but they kept me positive and really did everything they could. I will always be very grateful for their support.
"I wish everyone at Warriors all the best for the rest of the season and for what is going to be a very exciting period in the club's history."