The Raiders face a depleted Knights outfit at Newcastle on Sunday needing to win to keep their NRL finals hopes alive.

It's a team they've struggled against in recent years, losing four of their past six games, with Ponga a constant thorn in their side.

But the Newcastle captain's out for the rest of the season due to concussion.

He's formed a potent combination with Best down the Knights' left edge, but the centre and Enari Tuala have been left out of the side for failing to live up to team standards after missing the team bus in Brisbane.

It's part of the controversy that's descended on the Knights this week, with Ponga and Kurt Mann target-tested for illicit drugs following a viral video of the pair in a toilet cubicle.

The Knights have slumped to 14^th on the ladder, with only Gold Coast and Wests Tigers below them.

But Best's omission opened the door for Mapapalangi to make his debut.

That had Raiders second-rower Corey Harawira-Naera wary of Newcastle.

"I think they're giving a young kid a run up there. If we have a young guy debut it's a pretty special day for them so we try to get a win," he said.

"I think they'll be up for it because they want to make it a memorable one for him.

"I don't know what's happened with the other guys out, but I guess that's a shining light when you've got a young guy coming in and his dream's coming true."

In a boost for the Green Machine, Harawira-Naera was expecting star prop Joe Tapine (ribs) to be fit for Sunday.

His return will bolster Canberra's front row and has given them the luxury of dropping Ryan Sutton to the extended bench.

"He didn't look too good last week, but he's moving pretty freely today so positive signs," Harawira-Naera said of Tapine.

MORE RAIDERS NEWS

"I asked him and if he says he's sweet he's normally pretty sweet to go."

Josh Papalii said it was a massive boost for the Knights game and the pair would look to do some "damage" against Newcastle.

Tapine leads the NRL for post-contact metres, was third for offloads - with Papalii fourth - and the leading forward for run metres.

"Massive. No doubt he's been the in-form prop of the year. I don't think he's played a bad game all year for the Raiders," Papalii said.

"It's always good to get big Joe back. He's very damaging with and without the ball. Just can't wait to play alongside him again and hopefully do some damage."

Tapine's return was also timely from a defensive points of view.

Harawira-Naera said the space afforded to Ponga and Best that allowed them to hurt the Green Machine in previous encounters was down to the middles not doing their job.

He said they'd put a focus on slowing down the ruck speed this week by finishing their tackles properly.

The New Zealand international said they hadn't done that in the narrow win over St George Ilawarra on Sunday, which allowed the Dragons back into the game.

"[Ponga and Best are] probably their strike weapons out wide. We sort of struggle with their middle forwards when we come up against them," Harawira-Naera said.

"They normally get us in the middle and then spread it wide for those guys. That's one thing we're focusing on this week.

"The tries we let in last week we weren't putting guys on the deck and inside the 10m they were scoring most of their tries off that.

"That's something we've got to be aware of, finishing our tackles, especially when we're defending our line."

Meanwhile, the Raiders look set to announce fullback Xavier Savage's contract extension on Thursday.

Terms were agreed last week for a two-year extension believed to be until the end of 2025.

NRL ROUND 23

Sunday: Canberra Raiders v Newcastle Knights at Newcastle Stadium, 4pm.

Raiders squad: 1. Xavier Savage, 2. Nick Cotric, 3. Matt Timoko, 4. Sebastian Kris, 5. Jordan Rapana, 6. Jack Wighton, 7. Jamal Fogarty, 8. Josh Papalii, 9. Zac Woolford, 10. Joe Tapine, 11. Hudson Young, 12. Elliott Whitehead (c), 13. Adam Elliott. Interchange: 14. Tom Starling, 15. Emre Guler, 16. Corey Horsburgh, 17. Corey Harawira-Naera. Reserves: 18. Albert Hopoate, 19. Ata Mariota, 20. Matt Frawley, 21. Ryan Sutton, 22. Charnze Nicoll-Klokstad.

Knights squad: 1. Tex Hoy, 2. Edrick Lee, 3. Dane Gagai, 4. Krystian Mapapalangi, 5. Dominic Young, 6. Anthony Milford, 7. Adam Clune, 8. David Klemmer, 9. Jayden Brailey (C), 10. Daniel Saifiti, 11. Tyson Frizell, 12. Brodie Jones, 13. Jacob Saifiti. Interchange: 14. Phoenix Crossland, 15. Pasami Saulo, 16. Simi Sasagi, 17. Mathew Croker. Reserves: 18. Sauaso Sue, 19. Chris Randall, 20. Jack Johns, 21. Oryn Keeley, 22. Hymel Hunt.

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