Cronulla coach Shane Flanagan concedes it's unlikely co-captain Wade Graham will be fit to face Penrith in next week's NRL semi-final after he left Allianz Stadium on crutches.
Graham went for scans late on Saturday night after he limped from the field early in the first half of the Sharks 21-12 loss to the Sydney Roosters.
The key forward exited following a fumble and collision in the lead up to a Roosters try.
Graham headed straight up the tunnel and only emerged briefly in the second half on crutches, while Cronulla medical staff told the Nine Network there were characteristics of anterior cruciate ligament damage.
"He's going for a scan now," Sharks coach Shane Flanagan said post-match.
"It's hopefully not too bad, but those sort of things aren't a week."
The Sharks co-captain will likely only have six days to recover for the do-or-die Panthers clash, with the game expected to be scheduled at Allianz Stadium on Friday night.
The second-rower had already been battling an injury in the same strapped right knee, and missed a game with medial damage last month.
The 27-year-old has endured a frustrating season, having missed seven matches following hamstring, groin, concussion, knee and cheekbone issues as well as a suspension.
Saturday's injury came after Graham had earlier helped set up the Sharks' first try, when he flicked a ball on their left edge to Ricky Leutele before Sosaia Feki dived over.
Cronulla failed to make the most of subsequent chances, as they bombed three potential tries against a clinical Roosters outfit.
