Penrith's top-four hopes will rest on a halves pairing with just 42 NRL games between them after Matt Moylan was ruled out for two weeks with a hamstring injury.
Moylan won't play again before the NRL finals series after he suffered a hamstring complaint, understood to be different to the one that has troubled him in recent months.
It means 21-year-old Tyrone May will partner 19-year-old Nathan Cleary in the halves for Sunday's key clash with St George Illawarra, as the Panthers aim to keep their top-four hopes alive.
The pair have started together just three times in the NRL for three wins, after May made his debut in round 19.
The Panthers are trying to become the first team in the 109-year history of the competition to recover from a 2-7 start to make the top four.
They have been given a boost for the Dragons' clash with hooker Peter Wallace to return from a hand injury.
Meanwhile the flu-stricken Dragons have named Tyson Frizell and Nene MacDonald, despite both being injured in the lead up to last week's Brisbane loss.
Parramatta's top-four aspirations have also taken a hit, with fullback Bevan French ruled out for the final two round of the regular season with a hamstring injury, replaced by Will Smith at the back.
But the Eels appear likely to have Beau Scott (bicep) and Kaysa Pritchard (knee) back in time for the finals, named on the extended bench for Thursday's clash with Brisbane despite having what were thought to be season-ending injuries.
North Queensland's Gavin Cooper (calf) and Lachlan Coote (ankle) are also on the mend, named on the extended bench as they look to keep their finals fate in their own hands against the Wests Tigers.
Winger Antonio Winterstein has also been named at wing in place of injured star Kalyn Ponga, while John Asiata has been named on the bench despite an elbow injury.
Out-of-form Manly's push for a top-eight spot has also become harder, with the Warriors' Shaun Johnson cleared of a knee injury to line up alongside Kieran Foran (back) against them on Sunday.
Elsewhere Jarryd Hayne is back from a groin injury for the Gold Coast against unchanged Canterbury, but captain Ryan James won't play in the team's first game without sacked coach Neil Henry due to a shoulder issue.
Nathan Ross has also made a quick recovery from a fractured back to be named for Newcastle, while Bryson Goodwin will replace the NRL's leading tryscorer, Alex Johnston (hamstring) at fullback for South Sydney against Melbourne.
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