THE AFL's two hottest teams realise it will be 'game on' when the ball is bounced at Skilled Stadium on Sunday.

Reigning premier Geelong hosts North Melbourne – the team that in recent weeks has emerged as a genuine challenger to the Cats – in a battle of first versus fourth in a game the Kangaroos must win if they hope to cling to the double chance come finals time.

While the Cats, raging favourites to go back-to-back in 2008, have won 11 games on the trot, Dean Laidley's side has also built momentum with six straight wins.

Geelong defender Matthew Scarlett knows his side must continue the outstanding form it has shown in the second half of the season to maintain its unbeaten run.

"We'll need to play some of our best footy, because along with ourselves the Roos are the form team of the competition," Scarlett wrote in his weekly column on gfc.com.au.

"I think North Melbourne has improved a lot from 12 months ago. Obviously they copped a couple of beltings in the finals last year but everyone knows that isn't the true North Melbourne."

But while Scarlett is wary of a North side on the up, he said the Cats of '08 were also a better outfit than last year's model.

"While the Kangaroos have improved this year, there's no doubt that we have too," he said.

"We're playing better footy than we were last year and are a lot more confident in each other than we've ever been. Now we've just got to keep winning."

North Melbourne skipper Adam Simpson knows his team has a mountain to climb when it run out against the competition's benchmark side on Sunday.

"Every team, except for Collingwood, has struggled [against Geelong] this year and I think they've won 24 or 25 games out of 26," Simpson said at his team's open media session earlier this week.

"We've been in good form, we're proud about how we've gone about it, and Dean's coaching really well at the moment and we're following instructions.

"We've had a really good two months of footy but we're playing against a team that is pretty much undefeated for the last 18 months."

While acknowledging Geelong's impressive record, Simpson said his team would go into the clash believing it could win – with a narrow 13-point loss to the Cats in round 11 evidence the Kangaroos could mix it with the league pacesetters.

"They're not unbeatable … we're going to go down with plenty of confidence," Simpson said.

"The team's up at the moment, so I'm not going to come here and say we're going to lose, but I'm not going to come here and say we're going to go out there and smash them and take home the points."