Fremantle coach Ross Lyon wants his team to develop a ruthless edge – and it won’t be a comfortable experience.

For the first time in their history, Fremantle are unbeaten after four AFL rounds – but only just.

The Dockers led Sydney by 48 points at half-time on Saturday night, but that lead was whittled down to just three points midway through the final quarter.

A steadying goal to Matthew Pavlich was enough to lift Fremantle to a 11.8 (74) to 8.12 (60) win, but Lyon wants his charges to understand there’s no such thing as a “safe” lead in modern footy.

That point was rammed home in Saturday night’s other match, where Hawthorn almost pinched a win off Port Adelaide despite trailing by 58 points at one stage.

“You’re never safe. Not against quality,” Lyon said.

“You’re hoping to hear that siren while you’re in front.”

Sydney coach John Longmire agreed, but next time he wants to be the coach worrying about whether his charges can to hold on to a huge lead.

“The best advice would be to not get 50 points down,” Longmire said with a wry smile.

“You can’t afford to give anyone starts. You have to get things right from the very start, against any team – let alone the best teams.”

Fremantle led West Coast by 79 points in round three. But a second-half fadeout saw that margin trimmed to 30 by the final siren.

Lyon said it was imperative for his players to put away opposition sides when they have the chance.

“Human nature is once you get comfortable, everyone breathes out and relaxes a little bit,” Lyon said.

“And on the other side you feel like you need to get going. That’s about being a ruthless AFL team, and we’ve clearly got some work to do.

“I think we learnt that when challenged, we were able to get the momentum back. And (we also learned that) against quality you can’t relax for a minute.

“We’re really pleased we take the four points. We’ve got a lot to learn and we need to keep improving.”

Lyon scoffed at any talk he would rest players for Sunday’s MCG clash with Melbourne, who are 2-2 following their impressive win over Richmond.

Sydney face the Western Bulldogs at the SCG next Saturday, and Longmire said it was imperative for his team to stick their tackles from the outset.

“With our first half against Fremantle, we missed too many tackles,” Longmire said.

“The difference between effective and ineffective tackles is a key stat in football.”