For Kiwis' fans, there could be a downside to the Cowboys run through the NRL finals.

It's been a Cinderella run, and the North Queensland team have become the first team to reach the grand final from eighth position since the Eels in 2009.

Their unexpected success has been largely built around the incredible exploits of Jason Taumalolo, who has lifted another gear in the last few weeks.

The 24-year-old is surely the best impact forward in the NRL, and his ability to continually bend the defensive line has provided the Cowboys with constant momentum.

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Taumalolo has carried for more than 190 metres per game during the regular season, and has lifted that to an extraordinary 240 metres a match in the finals, as well as a large defensive load.

But at what cost? How much petrol will he have left in the tank for the World Cup, where he will be expected to be the cornerstone of the Kiwis pack.

Privately, the New Zealand selectors might have preferred if the Cowboys missed the eight - they only snuck in courtesy of the Bulldogs surprise win over the Dragons - so Taumalolo could put his feet up for a few weeks before beginning World Cup preparations.

Instead Taumalolo has been a magnificent, relentless, wrecking ball.

But his form brings back memories of 2015, when he anchored the Cowboys' run to their maiden premiership.

By the end of it he was physically and mentally spent, and was pulled from the Kiwis' tour of England by the Cowboys.

That's less likely to happen this year - given the importance of the World Cup - but can he lift himself for the massive challenges of that tournament?

Not just the possible semi-final against the English and hopefully another finals clash with the Kangaroos in Brisbane, but also two immensely physical challenges against the Samoa and Tonga.

The other concern for league fans on this side of the Tasman is the growing stature of Michael Morgan.

He's been playing so well that Cowboys fans have almost forgot about Johnathan Thurston, who has been sidelined since July and will miss the World Cup.

Losing one third of the Thurston-Cronk-Smith axis was supposed to significantly weaken the Kangaroos but the form of Morgan will soften the blow.

Morgan has been one of the most underrated players in the game over the past few seasons but he now looks ready to deliver.

He's surely a lock for the Kangaroos No6 jersey and offers a formidable array of attacking weapons, as well as a being a strong defender.