North Melbourne have replaced Fremantle as the side most likely to break into the AFL top eight, smashing the Dockers by 98 points.

The 21.17 (143) to 6.9 (45) result on Saturday night at Etihad Stadium was the Dockers' fifth-straight loss and they looked like a side that is limping to the end of the season.

The Kangaroos replaced Fremantle in ninth spot on percentage and the two sides are half a game behind eighth-placed Sydney, who host St Kilda in another big game on Sunday.

Young North midfielder Andrew Swallow was best on ground with 30, while Daniel Wells and Cam Pedersen also starred.

Pedersen and Aaron Edwards kicked three goals apiece and were among 11 Kangaroos goal scorers.

Dockers key defender Luke McPharlin, Nathan Fyfe and David Mundy were clearly Fremantle's best in a disastrous night for the club.

It was easily North's biggest winning margin this season, while it was the Dockers' lowest score for the year.

A behind after the siren meant Fremantle avoided equally their lowest score against North.

Adding to the Dockers' problems, captain Matthew Pavlich was subbed off late in the second term with what looked to be a calf muscle injury.

Small forward Hayden Ballantyne also limped off in the final term.

Clayton Hinkley appeared to be reported in the first term for high contact with North first-gamer Aaron Mullett.

While injuries have cruelled the Dockers' second half of the season, there was no excuse for the lack of intensity after the first few minutes of the match.

Fremantle did not kick a goal from 18 minutes into the first term, when they trailed by 11 points, until 12 minutes into the third quarter - by which time the margin was 53.

North's last two opponents are St Kilda and Richmond, while Fremantle will start at long odds against Collingwood at home next Friday night and then return to Etihad Stadium for the round-24 game against the Western Bulldogs.

Michael Johnson marked and goaled inside the first minute to give Fremantle the ideal start, but the Kangaroos responded immediately with two of their own.

Scores were level when Johnson lined up for his second, but sprayed the straightforward shot.

North sent the ball down the other end quickly for a goal, the first of three in a row to put them in control.

The only setback for North during the game was midfielder Jack Ziebell, who was taken to hospital for precautionary tests after he was subbed off with a chest injury.

Coach Brad Scott said it was a rare game where everything they planned turned out so well.

But he also sympathised with Fremantle's injury plight.

"It's very, very difficult from a coach's perspective when your players are running on empty, as it appeared the Freo boys were today," he said.

"But we could only hold up our end of the bargain and I thought we did that really well."

Timing is proving critical for these two teams - through the summer and the early part of the season, it was North struggling with a massive injury list.

Scott also said nothing had changed for North as they try to snare a finals chance.

"It's exactly the same as it was last week - we said we were going to make an assault on those three games and all that changes is we only have two games to do that," he said.

"We can only hold up our end and where that leaves us will be where we deserve to finish.

"I'm also really, really conscious that we have to be playing the sort of footy that is worthy of being a finalist team.

"There's no point in the eight and getting obliterated in the first week of the finals, so we still have to improve."

Fremantle coach Mark Harvey said skill errors had hurt his team, plus he was animated at three-quarter time as he demanded a better effort.

But personnel woes have left Harvey with limited options.

"The enormity of what we're dealing with at the moment, I've never seen it before, how many players are knocked up," Harvey said.

"A lot of them can't train during the week and they're just flat-out getting to the game.

"That's not a reflection of the margin, that's not discounting how good North Melbourne were tonight."

The Dockers confirmed hamstring injuries for Pavlich and Ballantyne while Hinkley was reported for rough conduct.

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