Saifiti has been named to replace his injured twin sibling, Daniel, in Newcastle's engine room for Saturday's clash with South Sydney at Bankwest Stadium. It will be the 24-year-old's first start in the run-on side since the last round of 2017, a span of 1050 days, or two years, 10 months and 16 days.

Injuries restricted him to just 15 games in seasons 2018 and 2019, and with one more year remaining on his contract, the Fijian international realised he had reached his career crossroads.

He has responded with form that has earned comparisons to NSW Origin representative Daniel, prompting Knights officials to table a two-season extension that is likely to be signed by early next week.

Daniel, who is out for up to six weeks with a knee injury, leaves behind big boots to fill, but Jacob boasts the same size-15 foot and Knights coach Adam O'Brien is confident he will relish the challenge of leading the charge alongside Test prop David Klemmer.

"I think when you're replacing Daniel, we've got one that's pretty close," O'Brien said.

"He's looking forward to starting a match. He's deserved it. His opportunity has come through an injury to his brother, but I would have had no qualms over the last eight weeks about starting with Jacob.

"He's worked really hard in the pre-season and I'm really looking forward to starting a game up front with Klem."

Jacob has played all nine games for Newcastle off the bench this season, averaging 116 metres in attack and 27 tackles per game.

His impact has been such that Klemmer said he would not be out of place packing down alongside his brother for the Blues at Origin level.

Yet it was only 12 months ago that Jacob was on the outside, looking in, after suffering a broken ankle in a much publicised off-field incident, an injury that sidelined him almost half a season.

Asked last week about the prospect of returning to the starting line-up, Saifiti said that would be "cool" but added: "i'd play wherever the team needs me.

"If it's orange peeler, I don't mind, as long as the team's winning ... I don't see myself taking it off those two [Klemmer or Daniel], with the quality footy they're playing.

"I'm happy to bring some energy off the bench."

Only 12 of Jacob's 63 appearances for Newcastle have been in the starting line-up. Daniel, in contrast, has been a run-on regular for the past three seasons and has not played off the bench since early last year.

Newcastle need a win against Souths to regain the top-four position they have held since round one.

The Rabbitohs have won four of their past five games but will field a reshuffled backline after the suspension of Latrell Mitchell and injuries to Campbell Graham and Braidon Burns.