Twelve of the 16 NRL teams named this week boast a fullback or five-eighth who have played both positions in recent times.

And Newcastle star Kalyn Ponga is the latest, making the anticipated switch in their round-one win over Cronulla.

But despite their early success, debate continues to rage over how long coach Nathan Brown will wait until he pulls the plug on his experimental spine.

Brown recognises that it's not only the Knights who are under the spotlight, with St George Illawarra counterpart Paul McGregor facing a similar headache.

"We saw a game (Thursday) night where they got two five-eighths who have played fullback and one's playing fullback," Brown told reporters on Friday.

"And it obviously generates plenty of talk. We saw (Canberra star) Jack Wighton play five-eighth last week, who's been at fullback for four years.

"So there's a lot of shuffling in this position at the moment."

Brown believes there are only two major factors when it comes to deciding on whether to persist with the new-look combination.

"Does the group want it to work, and does Kalyn want it to work?" Brown said.

"That gets a big tick on both fronts. The buy-in's good from the playing group and Kalyn really wants it to work, so it'll work over time."

Ponga's evolving combination with Mitchell Pearce will face a major acid test on Saturday when they host title hotshots Penrith.

Their battle with Panthers halves James Maloney and Nathan Cleary, who double as the NSW State of Origin pairing, shapes as a key battle.

While Maloney has had his defensive issues throughout his career, Knights legend Matthew Johns believes Ponga faces a different challenge when without the ball.

Johns pointed out how Ponga made four tackles in one set against the Sharks, and claimed his eagerness to work in defence would burn all his fuel.

"What Matty's saying is there's got to be a common sense factor," Brown said.

"Obviously Kalyn's number one asset for the team is an outstanding offensive player. And if he goes chasing too many tackles, well that can knock him around.

"He'll work it out over time.

"Good competitive players who were champions - the Johns', Alfie Langers, these blokes - when games need changing on the back of defence, they chase kicks and get to marker and do 2-3 in a row."

STATS THAT MATTER

* A Knights win would give the club back-to-back victories over Penrith for the first time since winning five straight from 2011-13.

* Ivan Cleary will coach his 100th match for Penrith, becoming just the sixth coach to do so behind Royce Simmons, John Lang, Matthew Elliott, Bob Bolan and Phil Gould.

* Penrith haven't won their opening away match of a season since 2012.

Australian Associated Press