Sydney Roosters winger Daniel Tupou will miss the next six weeks of the NRL because of a back injury he suffered in last week's State of Origin III.
The injury, a tear in the 23-year-old's Latissimus dorsi muscle, is identical to that which his Tricolours teammate Michael Jennings sustained in Origin II.
Jennings is expected to miss another three weeks while Tupou is likely to return only for the final two rounds of the NRL regular season when the premiers host Melbourne and then South Sydney.
Centre Shaun Kenny-Dowall said the loss of Tupou was a blow for the struggling Roosters ahead of Saturday's clash with top-of-the-table Penrith.
"Unfortunately he is going to miss five or six weeks, he is a great player and some of our young guys are really going to have to step up in his absence," said Kenny-Dowall.
"We have some great young guys coming through, young Nene [Macdonald] out there and Brendan Elliott, who made his debut last week, so we are going to have to work really hard on those guys and bring them up to NRL standard."
Macdonald shapes as the likely inclusion for Tupou against the Panthers.
Meanwhile, both Kiwi winger Roger Tuivasa-Sheck and captain Anthony Minichiello are likely to be fit for the round 19 Rise for Alex fixture.
Tuivasa-Sheck missed the Roosters' shock last-start loss to Cronulla with a hamstring injury. Minichiello suffered a hamstring injury against the Sharks.
Queensland back-rower Aidan Guerra didn't train with the Roosters yesterday after being rested but he will play on Saturday.