Lions scrumhalf Nic Groom has been ruled out for the remainder of the Super Rugby season as he undergoes surgery on an injured hand, the union confirmed on Tuesday.
The Lions are now thin on options in the number nine jersey behind Springbok Ross Cronje as they prepare to host the Jaguares from Argentina in their quarter-final at Ellis Park on Saturday.
Groom's place in the squad is likely to be taken by the inexperienced Marco Jansen van Vuren, who made his first start in the competition earlier this year in a 49-35 loss to the Jaguares in Buenos Aires in March.
The Johannesburg-based side signed Groom from English side Northampton Saints shortly afterwards in early April to add depth to their scrumhalf options.
The Lions have appeared in the last two Super Rugby finals, suffering an away defeat to the Wellington Hurricanes in 2016 and a home loss to Canterbury Crusaders last year.