Premiership-winning Newcastle legend Matthew Johns believes Kalyn Ponga can "be a Benji" and develop into one of the all-time great five-eighths - if the Knights keep the faith.

Johns is adamant Newcastle's NRL top-eight chances in 2023 hinge on the Knights giving Ponga sufficient time to make a successful transition from fullback to the second receiver role.

Former Knights mentor Nathan Brown aborted a similar operation just three games into the 2019 season and Johns is urging coach Adam O'Brien to hold his nerve even if the experiment doesn't again pay immediate dividends.

"It will take a bit of time. You've got to persevere," Johns told AAP.

"And at times they've got to find a way to, hiding him is not the right word, but finding a way that he doesn't make 40 tackles a game because that's what opposition teams are going to try to do.

"He needs a little bit of protection. You might defend him in the centres a bit. Not that he can't tackle, it's just that you don't want to be burning his petrol."

Darren Lockyer and Benji Marshall both made the successful switch from fullback to become Golden Boot winners as world players of the year.

Johns sees a lot of Marshall, in particular, in Ponga.

"He's so classy," he said.

"And Benji, when Benji was a young guy, he was just a pure runner who played a bit of fullback, just a freakish player like Kalyn, who really ended up being one of the great sixes.

"Now I don't want to sound like a broken record but of course if you tell me that Kalyn's going to have a good season, and plays 20-plus games, then I'm thinking we can fall into seventh or eighth. Around that bottom part (of the top eight).

"I'm a lot more optimistic than I was last year.

"Last year I saw a lot of injuries. I thought their roster was a little bit out of whack. This year they've stiffened themselves up a little bit in certain areas. There's a bit more depth in key areas."

Most significantly, Johns believes Newcastle's luring of former Australian sevens star Locky Miller from Cronulla to play fullback is a key to Ponga staying - and thriving - at five-eighth.

"I like Locky. I really liked what he did last year. He suits the way the game has gone," said Johns, Newcastle's greatest ever No.6.

"Traditionally, the way we think about the game, all the space is on the edges.

"But now the way the game has gone with the speed of the rucks, space is all through the middle. So he's a kid who just suits where the game is going.

"With Newcastle, if you've got Locky going through the middle, then you've got Kalyn coming off the back of it, then that's a big threat.

"At the moment, I can just see they're working out the nuances of all the combinations but I think they'll be a successful one. Locky's a really good buy."