Kalyn Ponga ruled out of Newcastle's round-three clash against Penirth, Daniel Saifiti confirmed to play

The Knights updated their squad list on Friday afternoon with Tex Hoy replacing Ponga at fullback in the only changed to the 17 players named earlier this week.

The first back-up players for the game are now Simi Sasagi and Sauaso Sue.

Earlier on Friday, Knights coach Adam O'Brien said he wanted to assess how Ponga pulled up from training later in the day.

The fullback missed last week's win at home over Wests Tigers after picking up a minor knee injury in round one against the Roosters.

"I think if he has his way, he will be playing. I know how disappointed he was last week," O'Brien said.

"I just want to have another look at him in the session today and I'll make a decision from there. It is early days in the season. But Daniel [Saifiti] is a definite starter."

Asked to describe how far off 100 per cent the Knights' skipper was, O'Brien said Ponga was "really close" to being a confirmed starter.

"If I left it up to him last week, he would have [played]," the coach said.

"It's my job, and the medical team, to protect them from themselves - they'll play in every game if you'll let them.

"He is very, very close."

O'Brien said he was impressed with Tex Hoy's performance against the Tigers.

"I thought Tex did a great job for us last week," he said.

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"The players around him did a good job to help him, but he was tough, did his job and was nice and safe at the back.

"So I would expect more of the same from Tex."

Saifiti's timely return from a knee injury helps cover for the loss of David Klemmer, who is set to miss at least three weeks following knee surgery.

The Knights also lost Lachlan Fitzgibbon this week for an expected two months with a medial ligament tear.

After replacing Fitzgibbon in the Tigers match, Mitch Barnett is set to stay in the back row. He had started last week at prop, where he also played against the Roosters.

"I like what Mitch Barnett has been doing through the middle, but we've had a COVID scare there with Brodie [Jones]. That will allow Barney [to play second row]," O'Brien said.

"He spent all of last year on that left edge, so it's not foreign to him."

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Penrith have also been hit by injuries to key players and confirmed Thursday that halfback Nathan Clearly and gun forwards James Fisher-Harris and Liam Martin would miss the game. Winger Brian To'o is also out.

But O'Brien said Penrith had already proved this year how dangerous they were without their star players.

"What Ivan and the coaching staff has been able to instil ... it's a system that holds them together," he said.

"You look at their [Cronulla] trial ... they were down on personnel there and they just managed to have some next-man-up mentality."

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The Knights have let in only one try in each game this season, and while O'Brien said it was hard to be critical of his side's defence, he thought the matches could have been shutouts.

"I was disappointed with the two tries that we've leaked late," he said.

"That is a sign that we've let scoreboard and the clock dictate our mindset, so we've spoken about that this week."

Kick off at Carrington Park is scheduled for 3pm.

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