Saracens lock Alistair Hargreaves has retired from rugby following a concussion injury.
The 30-year-old played 79 times for the north London side after joining from Super Rugby franchise Sharks in 2012.
Hargreaves, who won four international caps for South Africa, captained Sarries to the Premiership title in the 2014-15 season.
"After seeking medical advice I've come to the conclusion that the risk is outweighing the reward," he said.
"I've suffered a number of concussions in the last two seasons.
"Although this was a hard decision for me, personally it's one that I feel is the right one to make."
Hargreaves is the second player to retire because of concussion in recent weeks, following Ireland and Connacht prop Nathan White.
Listen to BBC World Service Health Check programme on concussion in sport here.