London - Newcastle forward Mouritz Botha has been forced to retire on medical advice after sustaining a serious concussion last season.
Capped 10 times by England, South Africa-born Botha opted to hang up his boots rather than risk further concussion issues in the future.
The 35-year-old spent two seasons with English Premiership side Newcastle after joining from Super Rugby outfit Sharks in August 2015.
Botha had previously played 142 games during six seasons with Saracens, who he helped win the Premiership title in 2011.
"Although many players have mixed emotions when they call time on their playing days, I only have one overriding feeling - that I was truly blessed to have had enjoyed my time as a rugby player as much as I have done," Botha said in a statement released by Newcastle on Tuesday.
"I am extremely proud to have been able to represent England, an honour that I will always cherish, and to have won the Premiership with Saracens.
"I was very lucky to learn from some amazing coaches who turned me from a semi-professional into an England international.
"It is for this reason I'm now pursuing a career in coaching. I want to give players the same experience that I had."