Mata'utia is awaiting the results of scans after suffering suspected medial-ligament damage in his right knee during Saturday's 38-12 trial loss to St George Illawarra at Maitland.

That means the three players competing for what would appear the last remaining position on Newcastle's forward rotation - Aidan Guerra, Herman Ese'ese and Saifiti - are all likely to make the cut for the March 14 season-opener against the Warriors.

Others including Josh King and Pasami Saulo will come into contention if they stand out in Newcastle's final pre-season hit-out, against Sydney Roosters at Central Coast Stadium on Saturday.

"There is only one more [trial]," Knights coach Adam O'Brien said.

"They need to get out there and make the most of their opportunities. Some guys that don't make that shortened bus [to Gosford], I'll still be looking at their attitudes and what they do at NSW Cup level. I want to see a response ... we're not a 17-man team. We're a club. I want everyone performing well."

Asked after Saturday's trial how many positions were still up for grabs, O'Brien replied: "It's hard to say. I'll need to sit back and have a look at the video to give a more accurate answer."

Saifiti has given himself every chance of joining twin sibling Daniel in Newcastle's round-one squad after an impressive pre-season, culminating in strong showings at the NRL Nines and against the Dragons last weekend.

"I feel like I'm in the mix," Jacob told the Newcastle Herald. "Adam has given me some good feedback. He's told me he's happy with how I've been going.

"This next trial against the Roosters is my last chance to put my hand up for round one. It's do or die for me, and hopefully I can play well and get rewarded with a spot for round one."

Saitifi has played in 54 NRL games but only 15 in the past two seasons, after a frustrating run of injuries.

He said this was his first uninterrupted pre-season since his debut campaign in 2016 and he felt much better prepared for the year ahead.

"It's a bit different to be having a full pre-season with no injuries or surgery," he said.

"It's the fittest I've ever felt, and now I have to transfer that to playing good footy."

David Klemmer, Daniel Saifiti, Jayden Brailey, Mitch Barnett, Lachlan Fitzgibbon and Tim Glasby would appear to pick themselves for round one, while Connor Watson is set to be the regular bench utility.

Skipper Mitchell Pearce, Kalyn Ponga, Hymel Hunt, Edrick Lee and Kurt Mann also shape as certain selections, which leaves centre as O'Brien's main dilemma, in the absence of Bradman Best (broken foot).

New recruits Gehamat Shibasaki and Enari Tuala both impressed against the Dragons but Tautau Moga is hoping to be available to take on the Roosters after recovering from a hamstring strain.