Ponga spent the first three games of the 2018 season at five-eighth at his own request before the experiment was deemed a failure and he returned to fullback.

On day one of the Knights' pre-season, former Sydney Roosters and Melbourne assistant O'Brien erased any uncertainty over where 21-year-old Origin star Ponga will play under his reign.

"He'll be our No.1," O'Brien said on Wednesday.

"I think locking him into a side at five-eighth, which usually happens in the modern game, they have the halves separated. I think that would be criminal to do that.

"In terms of fullbacks, he's elite, but he's nowhere near his ceiling yet.

"We need to keep coaching him and he's eager to learn in that fullback position. I see that as his best spot for himself and us.

"I'm not going to compare him to (Darren) Lockyer, but you can move to six later on. Let's be the best No.1 first off."

However, with no bona fide five-eighth with experience on the books, it's the one position O'Brien needs someone to "go and grab" in the pre-season to help Pearce steer the ship.

During the high points of last season Pearce claimed six straight man-of-the-match awards, but his form fade coincided with the Knights' season collapse.

"There's a heavy reliance, I feel, at the moment, on Mitchell," O'Brien said.

"We need to move away from Mitchell needing to be a nine out of 10 for us to win. We need to improve everyone in and around Mitch to get the best out of him for the whole season."

The Knights are flush with utility players who have experience in the halves including Kurt Mann and Connor Watson - both of whom partnered Pearce at various points last season.

But it's an incoming rookie who has caught O'Brien's eye early.

Phoenix Crossland is seen as the long-term halfback for the Knights, but played just 12 minutes in his NRL debut in Round 16 last season.

"I really like the look of Phoenix Crossland, both physically and actually what he does with the game," O'Brien said.

"He's got a really good kicking game, a good strong passing game so I see him as an option."

Australian Associated Press