For decades, fans and pundits have searched for the secret ingredient in a premiership-winning team. Is it the superstar halfback? The dominant fullback? The coach?

After 40 years of watching rugby league, one truth stands out: the real common denominator is that premiership teams are made up of players all hitting career-best form at the same time.

Looking at the 2025 finals picture, it's clear that most of the contenders have followed this recipe. The question is: who can sustain it long enough to win the title?

The path to the grand final
The draw is set. The winner of Bulldogs vs Penrith will go on to play Brisbane in the preliminary final. The Broncos enjoy a week off and will be fresh. On the other side of the bracket, the Sharks face Canberra, with the winner to meet Melbourne.

Each of these six sides has an elite core. Each has players in career-best touch. The common denominator theory says the team that aligns most of these at the right time will win it all.

Penrith and Melbourne: Proven blueprints
Penrith remain the benchmark. From 2021 to 2024 they won four straight premierships by keeping their elites — Nathan Cleary, Isaah Yeo, Dylan Edwards, Brian To'o, Moses Leota, Liam Martin — consistent while surrounding them with breakout seasons from players like Matt Burton, Sunia Turuva, Paul Alamoti and Spencer Leniu. Ivan Cleary has mastered the art of refreshing the side without losing standards.

Melbourne are similar. For two decades they've built around elite anchors — Cameron Smith, Billy Slater, Cooper Cronk and now Cameron Munster, Harry Grant, Jahrome Hughes — while developing role players who peak at the right time. Bellamy's system makes the Storm the hardest team to put away in September.

Both clubs still have the hardest-to-beat DNA. They've proven it.

Brisbane: The threat from the north
The Broncos look primed. Payne Haas and Patrick Carrigan are elite forwards in peak form, while Kotoni Staggs is playing the best football of his career. Adam Reynolds and Ben Hunt bring plenty of grand final experience. The injury to Ezra Mam hurts, but their mix of hardened winners and hungry youth means they have the firepower to go one better than 2023.

With a week off and a home preliminary final, Brisbane are in the box seat.

Canberra and Cronulla: Dark horses rising
Canberra have justified their minor premiership. Hudson Young is playing his best football, Joseph Tapine remains elite, and players like Timoko, Tom Starling and Kaeo Weekes have stepped up. Then there is new sensation Ethan Strange who could get on a Kangaroo Tour. Their formline suggests they won't go quietly.

Cronulla started slow but are peaking at the right time. Nicho Hynes is close to his Dally M best, Trindall has hit career-best form at six, and the additions of Addin Fonua-Blake and consistent contributions from Mulitalo, Ramien and Brailey make them dangerous. They're not as proven as Penrith or Melbourne, but they fit the common denominator theory.

Canterbury: The newcomers to the model
The Bulldogs are trying to build what Penrith and the Roosters once chased: a strong elite core surrounded by breakout players. Stephen Crichton, Matt Burton, Viliame Kikau, Jacob Kiraz and Jacob Preston form that core. Around them, players like Connor Tracey, Kurt Mann, Max King and Sitili Tupouniua are hitting career-best form.

They might be a year or two away from being genuine favourites, but their progress into the top four shows they're on the right path.

Prediction: Who fits the recipe best?
History says the safest bet is to back the teams with proven elite cores and coaches who know how to get players to peak in September. That means Penrith and Melbourne are still the hardest to beat.

But this year feels wide open. Brisbane's mix of elite forwards, strike outside backs and veteran halves puts them right in the frame. Canberra and Cronulla fit the profile of dark horses, with multiple players peaking together. And the Bulldogs are closing the gap quicker than expected.

If the common denominator theory holds true, the winner of Bulldogs v Penrith could well decide who reaches the grand final. Whoever emerges will run into a fresh Brisbane side in the preliminary final, while Melbourne loom as the heavyweight on the other side of the draw.

Premierships aren't about one superstar. They're about seventeen players hitting peak form at the same time, anchored by a core of elites. In 2025, Penrith and Melbourne remain the standard, Brisbane are primed for a breakthrough, Canberra and Cronulla are live threats, and Canterbury are building fast.

On paper, the Panthers and Storm are still the hardest teams to beat. But if Brisbane's best players keep peaking together, the trophy could be heading north