Fonua-Blake, the former Manly enforcer, made a dominant debut for the Warriors in their 19-6 round-one win against Gold Coast last weekend, carrying the ball 202 metres, popping four offloads and effecting 22 tackles for good measure.

The Tongan international has troubled the Knights in the past, in particular in 2019 when his bulldozing runs inspired Manly to 26-18 and 30-6 victories over Newcastle.

But in Daniel Saifiti and David Klemmer, O'Brien knows he has two front-rowers highly motivated to give as good as they get against Fonua-Blake.

Both were outstanding in last week's 32-16 win against Canterbury, Saifiti scoring two tries on his captaincy debut, and Klemmer gaining 217 attacking metres.

O'Brien believes the key to countering Fonua-Blake is meeting his force with an equal and opposite reaction.

"You need to be committed," O'Brien said.

"He's a quality player, a really handy pick-up for the Warriors. He provides a lot for them in the middle and, like I said just then, you need to be committed to your contact with Addin."

O'Brien is eager for his troops to replicate the intensity they showed in their season-opening victory.

"It's important that we back up what we did last week," he said. "We had plenty of reasons to play well last week ... but it's important that we find that same desire this week and back up that performance."

O'Brien was delighted with the win - especially with key players like Kalyn Ponga, Blake Green, Lachlan Fitzgibbon and Edrick Lee unavailable through injuries - but felt there was still plenty of room for improvement.

"I thought there were moments of the game where we dropped off on some of our support play," O'Brien said.

"I think that needs to be a little bit more consistent.

"On a whole we were really pleased with our round-one performance. Naturally we're going to find things to get better at, but look, it's round two, so we're not the finished product yet."

The coach had no qualms about the likelihood of playing on a heavy track after torrential downpours on Thursday, with more rain forecast.

"We're pretty accustomed to what wet-weather footy looks like ... look, they're professionals and they understand what it takes in wet weather," he said.

O'Brien said he would delay decisions on injured quartet Kurt Mann (knee), Connor Watson (ankle), Bradman Best (foot) and Starford To'a (shoulder) until the 11^th hour.

"We've got a session today and we don't need to make a full decision until tomorrow, so we'll use all the time up on all three of those guys ... we'll wait until tomorrow afternoon and make a decision on all three," O'Brien said.

"big challenge"

"There's some match-ups right across the park," O'Brien said.

"Obviously the two forward packs, a lot's been spoken about the job that they did last week.

"Both teams completed really highly.

"Both teams have strong outside backs