Kalyn Ponga starred, but was then taken off with a right shoulder injury as Newcastle confirmed finals football with a brilliant 32-6 victory over Cronulla-Sutherland at Hunter Stadium on Sunday night.

Ponga scored one try and played a starring role in three others, only to leave the field late in the contest. 

The Sharks scored first through Connor Tracey, but a Bradman Best double and tries to Dom Young, Greg Marzhew and Dylan Lucas sealed victory for the Knights, who leap-frogged the Sharks into fifth spot on the ladder with a game to play, ending the Sharks faint hopes of making the top four.

The only downer on an otherwise spectacular showing from the Knights fullback was a crushing late shot from Jesse Ramien that left him writhing in agony on the turf.

The injury appeared to be to Ponga's right shoulder, with Newcastle suspecting an AC joint injury and scans set to take place on Monday.

Ponga attempted to play on, but was clearly in pain and failed to play a role in the Knights subsequent set, before leaving the field to a standing ovation after Marzhew's bulldozing try sealed victory.

"I don't know," Newcastle coach Adam O'Brien told ABC Sport when asked about Ponga's prognosis.

Any enforced layoff for Ponga would be devastating for the Knights, who have ridden a wave off the back of his form to surge into the finals. 

Newcastle had already won seven games in a row to rocket into contention — but their eighth sealed their position in the eight.

"It's an unbelievable feeling," Best told ABC Sport.

"We've worked hard all year and we've come home strong. We're full of confidence."

Locked at 6-6 at half-time, the contest felt like a game that needed some magic to break it open — and fortunately Newcastle has a magician in its ranks.

A season for Ponga that started with fears over repeated concussions, saw him dropped by Queensland's State of Origin side and left him flirting with retirement aged just 25, is ending in the most spectacular fashion — with Newcastle's late run sending warning shots across the NRL.

Ponga was again at his electric best, running for 200 metres from 17 runs — none more spectacular than his mazy 55-metre effort that set up Best's first try after half-time.

Claiming the ball on his own 10-metre line, Ponga burst past two would-be tacklers with an ease that made a mockery of the iron-clad defence that had typified the contest for the preceding 50 minutes.

After weaving in-field, past another two Sharks, Ponga was eventually taken down on the Sharks 35.

The Knights fed off that momentum-shifting run, Best being sent over to give Newcastle the lead for the first time in the match.

Ponga's charge was so spectacular because it was so rare in a game where both teams were locked in a grinding arm-wrestle.

In a gruelling first half, neither side were willing to budge an inch, with Newcastle twice denying Brit Nikora and Young in turn stopped from crossing twice by Braydon Trindall's brilliant covering tackles.

Tracey scored the first, scooting over after a well-worked move down the right, only for Newcastle to hit back through Ponga, who ghosted into the line and breezed through the defence on the left edge.