Fremantle rising star Heath Chapman says a tight bond and a jovial atmosphere have been the keys to the club becoming the stingiest defence in the AFL.

The second-placed Dockers (7-1) have conceded an average of just 57.4 points per game this season.

The next best defensive record is held by ladder leader Melbourne, which has conceded 61.1 points per game.

Chapman has emerged as a key part of Fremantle's defensive unit this season alongside the likes of Hayden Young, Luke Ryan, Alex Pearce, Brennan Cox and James Aish.

Fremantle's frenetic pressure further up the ground has helped the defensive unit, with the team now shaping as a genuine premiership threat following its stunning start to the season.

Chapman praised the way the defensive unit is working together.

"We’ve got a really good back seven, a real strong connection off the field, which I guess translates to having trust in each other on the field each weekend," Chapman said.

"We all go out there and have fun.

"We’ve got some good personalities back there, always having a laugh, not taking it too seriously, and sticking to our process.

"I think that holds us in pretty good stead."

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Fremantle will be aiming to continue its hot form when it takes on Gold Coast at Metricon Stadium on Sunday, but it will be without small forward Sam Switkowski (concussion).

The Suns (3-5) are coming off a shock 14-point win over Sydney.

Chapman suffered a season-ending shoulder injury in round seven last year, cutting short what was shaping up to be an impressive debut campaign.

The 20-year-old has seamlessly slotted back into the team this season, and he earned a NAB AFL Rising Star nomination for his 25-disposal effort against North Melbourne last week.

"I was pretty unfortunate to have an early injury in my career like that," Chapman said.

"But I was able to take some good learnings out of that, and prepare my body a bit better for the level.

"Now I don’t take games for granted. I try to do my best each week."

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