Munster have confirmed that second row RG Snyman tore his anterior cruciate ligament for the second time in just over a year.
The 26-year-old picked up the injury in yesterday's 43-13 win against the Scarlets in Llanelli, which had been the third game of the South African's comeback.
Snyman appeared to suffer the injury as he was tackled in the 60th minute, having caught the restart after Liam Coombes's second try of the game.
The player was helped from the pitch immediately, with head coach Johann van Graan telling RTÉ Sport after the game they feared his injury was "significant".
Those fears have now been realised, with the province confirmed that scans have shown the player has ruptured his ACL.
"We are all hugely disappointed for RG," Van Graan said.
"After doing everything that was asked of him and working so hard to get back into great shape everyone feels for him right now.
"While this is a setback, we know RG is young and resilient given everything he has gone through in the last year so there is a strong sense of perspective here.
"We have seen what other world class players have done in this position before and they have come back to reach the successful heights of their careers and I would expect no different for someone of RG's class and standing."
The player will now meet with a specialist to discuss surgery, with the province yet to put a timeline on his return.
"Here I go again, #Round2fight," wrote Snyman on Instagram.
RG Snyman limps off shortly after coming on as a replacement. Let's hope that the Springboks lock’s injury is not serious #SCAvMUN #RTERugby #RTESport https://t.co/JrzrUD5l3M pic.twitter.com/ioisL19Hgg— RTÉ Rugby (@RTErugby) October 10, 2021
The World Cup winning second row has endured a luckless time since he joined the province in the summer of 2020, suffering his initial ACL injury just seven minutes into his debut against Leinster that August.
He appeared to be close to a return in the Rainbow Cup, before a setback in his recovery in May.
A month later, he and three teammates suffered burns in a domestic accident, which further delayed his recovery, before he finally returned to action against the Sharks last month in the opening round of the United Rugby Championship.
The province had been slowly building his game time this season, with the lock playing 16 minutes and 23 minutes respectively against the Sharks and Stormers, before re-injuring his knee just nine minutes into his latest appearance.