But Cronulla coach John Morris believes he has the formula to break a side he deems genuine top-four material when they face off on Saturday.

Morris identified the Panthers' defence this year as the reason why they're currently sitting alongside the Sydney Roosters, Parramatta and Melbourne.

"They've clearly got some attacking weapons in their side, but what's impressed me most about Penrith is they've really tightened up defensively," Morris said.

"They're only giving away under 14 points a game."

Not since the Panthers conceded 11.4 points a game in 1991 has a team from the foot of the mountains been so stingy in defence.

Last year - Ivan Cleary's first in charge since his controversial return to the club - the Panthers were giving up almost 20 points per game and missed the finals.

But now his side hasn't given up more than two tries in their past five games.

Morris, whose side has racked up 80 points over the past two weeks, reckons he knows the best way to unlock the league's most improved defence.

"Value possession and make sure we're taking some energy out of them by dominating possession," he said.

"That goes a long way of getting a little bit of fatigue into their defensive line. Then you bring the six-agains into the game, you get a little bit of adlib footy.

"And that's when we can bring our attacking weapons into the game like Shaun Johnson, Wade Graham and Josh Dugan's been going really good for us."

Johnson in particular could be the key, having shot to the top of the league in try assists to be equal second on the Dally M leaderboard.

Cleary is no stranger to the threat of Johnson, with the pair combining to steer the Warriors to the grand final almost 10 years ago.

"I love watching him play. Hopefully I'm not enjoying him too much tomorrow. But he's one of those guys like a lot of talented ball players," Cleary said.

"You've just got to try and minimise the impact he can have in the game.

"It's more how well we can play our whole game, rather than specifically trying to stop him, because when he's at his best he's extremely hard to stop."

Penrith have lost Brian To'o (ankle) and Zane Tetevano (back) to injury, with Brent Naden and Spencer Leniu taking their place.

Cronulla winger Ronaldo Mulitalo comes in for Matt Moylan (hamstring).

STATS THAT MATTER

* Penrith are aiming for back-to-back wins over Cronulla for the first time since 2010.

* The Panthers are conceding a league-high 5.8 ruck infringements per game, while the Sharks have scored a league-high seven tries from six-again calls.

* Penrith are conceding the fewest tackles inside their own 20-metre zone, fewest points in the opening 20 minutes and equal fewest linebreaks in the league.

Australian Associated Press