The Eagles' club champion was taken from the ground on a stretcher immediately after snapping the opening goal of the third quarter, clutching at his groin.
West Coast, which had already lost midfielder Chris Masten to a knee injury halfway through the opening term, entered the final break two points behind but defied the injuries to prevail 13.14 (92) to 13.10 (88) in the stifling Perth heat.
North Melbourne entered the match without a ruckman after Todd Goldstein was withdrawn late with a stomach bug, leaving debutant Cameron Pedersen to go head-to-head with champion big man Dean Cox.
Pedersen was brave, but Cox was magnificent in a best-on-ground performance that confirmed his return to peak fitness after two injury-scarred seasons.
The four-time All Australian suffered cramp and was forced to play out the last quarter as a deep forward, but his 29 disposals, 29 hit-outs and two goals were the most telling contribution in the Eagles' first round-one win since 2008.
Temperatures peaked at 34 degrees in Perth on Sunday, and the final match of the opening got under way with the mercury nudging 29 degrees.
North Melbourne was celebrating 150-game milestones for Daniel Wells and Michael Firrito, and Brad Scott's men made the brighter start, kicking the opening three goals.
Despite missing important key defender Nathan Grima (back), the Kangaroos were controlling the early aerial battles in their backline, with Robbie Tarrant impressive all day opposed to Josh Kennedy.
Andrew Swallow was a star in the midfield for the Kangaroos, while Lindsay Thomas booted four goals. But their efforts were not enough, despite West Coast being down to 20 fit men.
Mark Nicoski booted two goals in the thrilling final quarter, while midfielder Luke Shuey again justified his high rating, drawing a free kick and sealing the win with a long-range set shot.
Influential players
Alongside Cox in the midfield for most of the day, Andrew Embley was superb for West Coast, with 28 possessions (10 contested). Stoppage specialist Matt Priddis led his side with seven clearances, while Mark Nicoski kicked 2.5 and had eight inside 50s in a half-forward role.
Swallow, opposed to Scott Selwood, was North Melbourne's best midfielder with 26 possessions (14 contested), while Thomas looked like turning the game in North's favour with two goals in a minute late in the third term.
Key match-ups
Adam Selwood didn't leave North Melbourne champion Brent Harvey's side on Sunday, restricting the influential Roo to 11 possessions and a goal. Given Harvey had racked up a massive 44 possessions when these sides met in round three last year, it was a significant defensive job.
What it means
West Coast's young players can draw confidence from their ability to outrun their opponents late in the game. That, coupled with a more organised defensive zone and improved disposal, will give the 2010 wooden spooners hope, but injury to the irreplaceable LeCras is a cruel blow.
The next four
West Coast: Port Adelaide (AAMI Stadium), Sydney Swans (Patersons Stadium), Hawthorn (Aurora Stadium), Melbourne (Patersons Stadium)
North Melbourne: Collingwood (Etihad Stadium), Fremantle (Patersons Stadium), Richmond (Etihad Stadium), Port Adelaide (Etihad Stadium)
New faces
West Coast unveiled two debutants in the same match for the first time in John Worsfold's 10-year reign, with midfielder Andrew Gaff and burly utility Jack Darling both solid. Gaff came on as the substitute in the second term and was influential in the final quarter with seven polished possessions. New Roos Pedersen and Cameron Richardson held their own, with Shaun Atley quieter on debut.
Dream Team highlight
Fantasy coaches may again start viewing Cox as a must-have after racking up a massive 142 points on Sunday. The star ruckman played loose behind the ball all day, with Pedersen doing likewise for North.
What the coaches said
John Worsfold (West Coast)
"It was a really intense win for us, so very proud of the way the players held up in a lot of individual efforts in terms of taking up a fair bit of the workload so we could keep some rotations going."
Brad Scott (North Melbourne)
"Clearly we were in the game right to the end and we could have snatched it, but full credit to West Coast. I thought they were terrific. I thought it was brave from our guys, but terrific from West Coast. They were really impressive and showed a lot of character."
West Coast 3.7 6.10 9.12 13.14 (92)
North Melbourne 4.3 6.5 10.8 13.10 (88)
GOALS
West Coast: LeCras, Darling, Cox, Nicoski 2, Priddis, Ebert, Embley, Kennedy, Shuey
North Melbourne: Thomas 4, Edwards 3, Adams 2, Harvey, Hansen, Anthony, Wells
BEST
West Coast: Cox, Embley, Adam Selwood, Priddis, Shuey, Darling, Nicoski
North Melbourne: Swallow, Thomas, Adams, Firrito, Pedersen, Tarrant
INJURIES
West Coast: Masten (knee), LeCras (groin), Nic Naitanui (shoulder) replaced in selected side by Nicoski, Patrick McGinnity (foot) replaced in selected side by Gaff
North Melbourne: Goldstein (illness) replaced in selected side by Ben Warren
Reports: Nil
Umpires: Margetts, Dalgleish, Schmitt
Official crowd: 35,878 at Patersons Stadium
The views expressed in this article are those of the author and not necessarily those of the AFL or its clubs
