Endurance king Andrew Gaff believes West Coast’s fitness could be telling late in games as executing skills under fatigue becomes a key factor again.

The League’s decision to reduce quarters to 16 minutes plus time-on last year suited power athletes, however the reduction in interchange from 90 to 75 per game and return to 20-minute terms tested players aerobically in round one.

Playing in oppressive conditions on Sunday, the Eagles found another gear and overran a determined Gold Coast outfit at Optus Stadium in the final quarter, kicking five unanswered goals to come from seven points down and win by 25.

Speaking on SEN, Gaff was confident another pre-season, albeit shortened, spent training in Perth's summer heat would hold West Coast players in good stead.

“We feel like we’re a fit side,” Gaff said.

“We obviously have pre-season in the heat where it’s (often) 35 degrees as it was on the weekend and we feel like we’ve got a good aerobic base, which is the way the game is definitely going with the longer quarters.

“We feel definitely in the midfield group but the half-forwards and half-backs we feel like those guys are as fit as the half-forwards and half-backs at any team in the comp.

“It’s about executing it under pressure and it feels like the back end of quarters they go forever a bit at the moment.”

As expected, the Suns posed a stiff challenge in the opening round and West Coast’s task doesn’t get any easier this Sunday in the club’s first trip to Melbourne since the 2019 semi-final to face the Western Bulldogs at Marvel Stadium.

The Dogs' vaunted midfield led the charge in their victory over Collingwood, with Bailey Smith, Jack Macrae, Lachie Hunter, Josh Dunkley, Marcus Bontempelli, Tom Liberatore and Adam Treloar sharing in 206 disposals.

The Dogs won contested possessions by 25 against the Pies, and dominated uncontested possessions by a whopping 124.

Ruck recruit Stefan Martin (15 disposals, one goal) also proved a valuable addition alongside emerging star Tim English (14, one), and the performances of Eagles duo Nic Naitanui and Nathan Vardy will be key to Sunday's result.

“They’ve got good names all over the park,” Gaff said.

“They’ve all been very good players for a long period of time and they’re hard to beat.

“It should be pretty even in the sense of two quality ruckmen on each side.

“The game will be obviously started in the middle with Nic against Martin and we hope Nic can get on top and replicate how good he was last year.”