Paul Gallen and Andrew Fifita will have to push through the pain barrier to ensure Cronulla are not missing more than 55 Origins and 1000 NRL games of experience in Thursday's grudge match with Penrith.

Both star forwards have impressive track records in playing through injury, Fifita soldiering through knee bone bruising that left him unable to walk for days at a time between games last year.

The pair will have to prove their fitness in a five-day turnaround for the Sharks, with Gallen eyeing a return from rib cartilage damage that has sidelined him for the past fortnight.

The 37-year-old veteran will require pain-killing injections if he's to take the paddock against the Panthers, and won't partake in any contact training having worn a no-contact bib during Monday's field session.

Fifita meanwhile was in rehab alongside Josh Dugan (general soreness) and Kurt Capewell (calf) while the first grade squad trained.

But teammates reported that the Tongan powerhouse was confident of overcoming the hamstring issue he picked up late against the Roosters.

The Sharks will need all hands on deck after two straight losses, with rep stars Aaron Woods (foot), Matt Moylan (hamstring) and Wade Graham (ACL) all still at least another month away from returning and if combined with Gallen and Fifita amounting to over 1000 games of experience on the sidelines.

"Fingers crossed I'll be right by Thursday," Gallen said on Monday.

"I'd say I'm a 'probable' this round. Without doubt, I was a possible [prior to missing last week's loss to the Roosters].

"I did a little bit of contact before the game and I just didn't pull up any good the next day on game day.

"I'll probably have painkillers without a doubt, that will last for a couple of weeks.

"But there's not too many guys going into games these days without something wrong with them so fingers crossed I get through OK … it'll be two and a half weeks by the time I play [since suffering the injury] so I should be right."

Moylan's hamstring injury is expected to sideline him until round 10, making for eight weeks since he first went down against the Titans, while Graham is targeting a round 11 return in a local derby with St George Illawarra.

Both the Sharks and Panthers have been slow out of the blocks to start 2019, sitting ninth and 11th respectively with 2-3 records.

But Gallen came to the defence of opposition playmakers James Maloney and Nathan Cleary, who have worn the brunt of criticism at Penrith and are in the firing line as far as their NSW Origin incumbency is concerned.

Luke Keary is firming for an Origin debut after a man of the match display against Cronulla last weekend, but Gallen said the Panthers pair still have plenty of time to turn their form around before June 5's series opener at Suncorp Stadium.

"At this stage [Keary's form] is undeniable," Gallen said.

"But for me the two halves from last year have got both feet in the door at the moment and it's going to take a big effort to move them out considering we've only won two series in 13 years.

"Keary's doing everything at the moment to kick one of them out. Who that is, we don't know. Jimmy obviously wants to play better, we all want to play better.

"I wouldn't be jumping to conclusions too quick just yet. Let's give them another four or five weeks and see where the competition's at then."