ADAM Simpson believes West Coast's spirit and unity, fostered since a talk from Australian cricket mentor Justin Langer before last year's finals, was the catalyst for the Eagles' stunning Grand Final comeback as they captured the club's fourth premiership. 

The Eagles ran a theme of "head, heart and gut" throughout the season, with gut focusing on digging deep when faced with adversity in final quarters.

West Coast never needed to call on that more than in Saturday's decider, after pulling off a brilliant fightback from 29 points down to be deadlocked with Collingwood by the last change.

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The Pies burst out of the blocks in the final term, booting two goals in as many minutes, but the Eagles stormed home.

Dom Sheed was the hero with the go-ahead major in the dying stages, before West Coast held on for an unforgettable five-point victory.

"We've had a bit of a theme about head, heart and the gut," Simpson said post-match.

"The heart is the love of the game, which we all love the game, and the gut is about the last quarter – and the instructions (at three-quarter time) weren't too much outside of that.

"Your head is your mental prep, and we've been working hard on that as well.

"The harder you prepare and the better you prepare the more you can go into a game with real good confidence."

Few Eagles looked confident in the nervous opening term, when several defenders – including skipper Shannon Hurn and youngster Tom Cole – had moments they would rather forget.

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"We thought our backs struggled a bit in that first quarter," Simpson said.

"I thought the midfield battle we won most of the day. I haven't seen any stats, so my gut tells me that we probably held sway in the middle for almost all the day.

"Our backs just didn't win a couple of crucial contests in the first quarter and some opportunities missed at goals.

"Their pressure was elite … and every mistake we had to pay for. But the numbers at quarter-time weren't horrendous, it wasn't like the midfield needed fixing or the forwards or the backs.

"It was just keep persisting."

Lewis Jetta dons the shades as he soaks in the flag win with his daughter. Picture: AFL Photos

West Coast never stopped believing and Sheed stood tall when the time came, putting the Eagles ahead after they had wasted numerous opportunities, booting 3.6 for the quarter.

"It (Sheed's goal) was a probably a product of all the work we did after the first 20 minutes," Simpson said.

"These things happen sometimes when you miss some, not straightforward goals but gettable goals and then someone kicks a goal like that.

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"I thought he might have actually played on, Dom, so to kick a drop punt all I did was look at the crowd when he kicked it and then when went into a different mode in the box."

Simpson was "blown away" to join Mick Malthouse and John Worsfold as a West Coast premiership mentor, and lauded his players' resilience during a testing year.

Losing Nic Naitanui (knee) and Andrew Gaff (suspension) was supposed to be a killer blow for the Eagles' flag hopes, but they fought on, with Sheed stepping up after Gaff was rubbed out after round 20. 

"I felt we had something going at the end of last year," Simpson said.

"Justin Langer spoke to our group … he spoke about spirit and it was probably the last piece for us from a club point-of-view.

"We tried to make the club a real sanctuary for the players, they're under a lot of pressure.

"We changed the attitude a tiny bit and the players responded so well, and I'm not surprised they did what they did today."

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Luke Shuey was outstanding in the midfield, racking up 34 touches and booting a goal to claim the Norm Smith Medal, and Simpson lauded star defender Jeremy McGovern, who finished with nine marks after spending time in hospital last weekend.

Simpson wasn't surprised McGovern, who plays sore regularly, was able to overcome his injury worry and take a match-defining intercept mark in the final term.

2018 premiership coach Adam Simpson, and premiership captain Shannon Hurn. Picture: AFL Photos

"He's an old-school footballer, not the way he plays, but he loves his mates, he loves a beer, when the time is right, he has passion for the club and that's why he's in our leadership group," Simpson said.

"Those type of things make you feel like you can back those guys in on the big occasion, because they will do whatever it takes."

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Simpson, who wasn't sure if restricted free agent Gaff had played his last game for the club, said the star onballer would remain "one of us" regardless of his decision.

First-choice Eagles Gaff, Naitanui, Brad Sheppard (hamstring) and Eric Mackenzie (toes) were on the fringes as West Coast's players celebrated in the rooms post-match.

"You can only imagine how Eric Mackenzie, Brad Sheppard, Nic Naitanui and Andrew Gaff are feeling," Simpson said.

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The Eagles coach, a dual premiership player at North Melbourne, didn't even know how he felt after winning a flag in his fifth season in the west.

"It's always been about the players and what they need to do to get right," Simpson said.

"Now I've just got this massive honour to represent this club and we can't wait to get home because I think there's going to be a pretty big parade coming for us."