Sharks second-rower Wade Graham said the State of Origin star would be a "big loss", but he was confident they could cover his absence if he doesn't play.

Gallen didn't train on Friday due to a sore back and remained in Sydney for further treatment.

The veteran has played 277 NRL games, 32 Tests for Australia and played 24 Origins for NSW.

His no-show would mean fans would miss out on seeing him and Raiders forward Josh Papalii renew their infamous rivalry, which erupted when Gallen accused Papalii of a "dog shot" four years ago.

Sharks coach Shane Flanagan named an extended bench on Tuesday, which included second-rower Kurt Capewell as 18th man.

"No doubt he'd be a big loss, [but] we've trained for it before, we've played games without Gal before and we've certainly got all the confidence in the players that have come in for him," Graham said.

"It's no excuse for us, we're looking to go out there and get the result regardless of who plays."

Graham said Gallen's experience meant he would have the best possible chance of taking to the field.

"[It was] just a bit of a back complaint so probably not the best for him to jump on a bus right now to come down with us," Graham said.

"He's going to get more treatment and see how he pulls up in the morning and hopefully he comes down in the morning and he's right to play. He didn't train today so he'll just have to take it by how he feels ... we've all got our fingers crossed and hopefully he comes through."

The Sharks have stumbled into the qualifying final having lost four of their last five games.

That late-season loss of form saw them slip out of the top-two, despite enjoying a 16-game unbeaten streak earlier in the year.

Graham was confident they could turn their form around, while Raiders captain Jarrod Croker still thought the Sharks were a genuine threat.

Croker said they had "plenty of experience and plenty of representative players", both in their backline and their forwards, and knew what "big games were about".

He said the Sharks would be a different proposition with hooker Michael Ennis, who missed the last meeting between the two teams due to illness.

Croker said Ennis was the key to the Sharks backline, which includes fullback Ben Barba and centre Jack Bird, firing.

"He's massive, mate. He's probably the key to a lot of their success and a lot of their momentum," he said.

"He gets the big fellas going forward and they create the opportunity for the halves and the likes of Barba and Jack Bird. He was sorely missed when he didn't play and he'll be a massive difference for them."

Croker also thought Barba was back to his 2012 Dally M Medal form.

Croker said limiting Barba's opportunities was vital to Canberra's chances of progressing straight to the preliminary final. The Raiders are the only club yet to make a preliminary final since the inception of the NRL in 1998.

"It's pretty hard [to contain Barba]. He's a good player, I think he's up there with the year he had a couple of years ago [when he won the Dally M], so there's no denying that and there's no doubting he's a fantastic player," Croker said.

"For us it's just about nullifying his opportunities and working hard together to keep that line because you give him a broken line and it's just about all over."

NRL QUALIFYING FINAL

Saturday: Canberra Raiders v Cronulla Sharks at Canberra Stadium, 5.30pm. Live on Fox Sports 1.

Raiders: 1. Jack Wighton, 2. Edrick Lee, 3. Jarrod Croker, 4. Joey Leilua, 5. Jordan Rapana, 6. Sam Williams, 7. Aidan Sezer, 8. Junior Paulo, 9. Josh Hodgson, 10. Shannon Boyd, 11. Josh Papalii, 12. Elliott Whitehead, 13. Sia Soliola. Interchange: 14. Kurt Baptiste, 15. Luke Bateman, 16. Clay Priest, 17. Joe Tapine, 18. Paul Vaughan.