Western Force flyhalf Peter Grant has been forced to retire because of a series of head injuries.
Grant, who notched five Tests with the Springboks, has suffered a number of concussions throughout his career.
The 34-year-old was keen to play on with the Force in the revamped Global Rapid Rugby, but specialists advised him it was best to retire.
"Initially it was shock and then disappointment and uncertainty because this is all I know, and I was really getting geared up for another season," Grant said.
"You go through the phases and there is a lot of emotion about that."
Grant, who intends to stay in Perth with his family, made his Force debut in 2016.
The versatile playmaker also amassed more than 880 points for the Stormers over 10 years, making his Test debut for South Africa in 2007.
Western Force coach Tim Sampson said Grant's forced retirement was upsetting.
"The recent news was devastating for every member of the squad and staff and naturally our thoughts are with Peter and his family," Sampson said.
"Within our program and during games, Peter was a calming influence on those around him, so to lose someone of Peter's experience leaves a huge void.
"It is never nice to see a player's intended retirement plan taken out of their control and dictated by injury."
Global Rapid Rugby is set to launch later this year, with eight teams to compete in a competition that will feature experimental rules and 35-minute halves.
The tournament winner will receive $1 million in prize money.
