FORCING Jeremy McGovern to play on a dangerous forward could be a key to unlocking West Coast's defensive masterplan, a rival assistant coach says.

The second-placed Eagles have confounded their critics this season, with coach Adam Simpson's rolling zone protecting an undersized backline and winning admirers.

After a defeat to West Coast in round 12, Richmond coach Damien Hardwick marvelled at Simpson's blueprint to cover for the loss of tall defenders Eric Mackenzie and Mitch Brown to season-ending knee injuries.

"To give up 23 marks to the opposition from our boot is credit to West Coast. They're doing some unbelievable stuff behind the ball," Hardwick said.

"Their zoning behind the ball is as good as we've seen this year and we struggled to get through at times."

West Coast's defence – with 195cm swingman McGovern at its heart – has leaked the fewest points of any side except Fremantle this season, conceding less than 68 points per game.

The makeshift backline has been protected by red-hot pressure on the ball-carrier, forcing opponents to bomb down the line into their waiting net.

West Coast is the League's No.1 intercept marking team (taking 17.2 per game) and is ranked equal fourth for intercept possessions (66.2).

McGovern has been the launching pad across half-back. The former rookie's taken 47 marks from opposition kicks, with veteran Sam Butler (24) the next best Eagle.

McGovern, 23, is also West Coast's leading intercept possession winner (103), ahead of a rejuvenated Sharrod Wellingham (86) and the much-improved Brad Sheppard (68).

One school of thought is that by taking away the big Eagle's opportunities to drop off his man, opponents could remove the central plank in West Coast's defence.

"You've got to make McGovern defend, he's become an elite player dropping off and intercept marking," an assistant coach told AFL.com.au.

"You've almost got to play a decoy forward on him or defend against him so you don't allow him to mark.

"Your forwards have almost got to hold (their position), make them defend and get in dangerous positions, and back-in your midfielders and defenders when they win the footy to be able to get the ball through.

"What's happening at the minute is that opposition (forwards) are pushing right down and getting used on the way out but they can't penetrate the defence."

Currently, only the Eagles and Hawthorn are ranked 'premiership standard' for scoring – averaging more than 100 points for and less than 86 points against - by Champion Data. 

Fourteen of the past 15 premiership teams' scoring has fallen within those zones.

But Simpson has warned his undersized defence will be "exposed at some stage".

West Coast faces Adelaide at home this Saturday night, with crunch tests looming against top-four contenders Collingwood, Fremantle, Hawthorn and the Sydney Swans over the next five rounds.

It remains to be seen whether elite kicking teams, such as the Hawks, can breakdown Simpson's system. 

"That's where Richmond battled because they tried to get their way through but they kept butchering the footy with their short, 45 (degree angle) kicks, especially in the first half," the assistant coach said.

"But an elite kicking side would still get through them. 

"It's no disrespect, they've been able to get away with it, but they're still missing some quality players in their back half, so those guys could be found out stages. 

"Especially if (Shannon) Hurn and McGovern get taken out of the equation a bit." 

So do industry insiders believe the Eagles are contenders or pretenders? 

"Put it this way, if they keep winning at home they're probably going to finish top-four," said the assistant, who also lauded the Eagles' more balanced midfield for their rise up the ladder. 

"But when it comes to finals time I think they might be a little bit short - I think they're still 12 months away.

"Everyone's just waiting to fall away because of their defenders, but they're holding their own at the minute so good on them."