Barnett was sent off in Newcastle's 38-20 loss to Panthers in round three for an elbow to the head of rival back-rower Chris Smith.

Not only did Barnett subsequently cop a six-week suspension, but in his absence the Knights endured a seven-game losing streak that left them briefly last on the ladder.

Since returning, the 28-year-old has helped Newcastle win two of their past three games to underline his reputation as one of their most valuable players.

O'Brien said the round-three indiscretion was "all in the past now" and the Warriors-bound enforcer has done everything possible to make up for lost time.

"I think he's redeemed himself in the games he's already played with us," O'Brien said.

"He's been outstanding.

"He worked really hard during that period, and nobody felt it harder during the form slump we were in there.

"Barney took it really hard. But to see how hard he worked to ensure that he was in tip-top shape when he came back, he's only proven that. I think he's been one of our most consistent guys over the last few weeks."

Barnett's form since resuming has prompted a change in tactics as the Knights prepare to welcome back Kurt Mann, who has missed five games after suffering a burst blood vessel in his ankle.

Mann was used in the early rounds of the season as a ball-distributing lock, combining with Newcastle's halves and fullback Kalyn Ponga.

On Sunday, he has been named to return as bench utility, replacing Phoenix Crossland.

"It's probably an understated - that'd be the word - boost for us," O'Brien said of Mann's return.

"It allows us to return to what we spent the summer [working] on, which I thought we did in the first couple of rounds.

"We've really missed that through personnel changing ... getting Kurt back in, he'll get the best out of a lot of blokes around him."

Sunday's clash with the defending champions shapes as an ideal chance for Knights back-rower Tyson Frizell to push his State of Origin credentials.

Frizell was a standby player for Origin I, but after NSW's 16-10 loss on Wednesday, team changes are expected.

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