WEST Coast coach Adam Simpson will "interrogate" his players to find out why his side fell away so badly in its eight-point loss to Collingwood at Etihad Stadium on Sunday.

The Eagles led by 24 points early in the last term and with Darcy Moore (neck) and Travis Varcoe (elbow and concussion) both out of the game by early in the third quarter, it seemed they were destined to win and join three other teams with a 10-7 record.

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However, they were slaughtered in the contested possession stakes in the final term, losing that tally by 22 as a Jordan De Goey-inspired Magpies outfit pulled off a brilliant victory. 

A visibly disappointed Simpson said after the game he needed to find out what went wrong. 

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"We need to look at what happened, find out why, interrogate our players to a certain degree, see how they're feeling. We put a lot of things in place to get better in this area and we've still got a lot of work to do," Simpson said. 

West Coast is 4-5 in games decided by 13 points or fewer this season. 

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Some of the Eagles' best ball-winners were well held, with Matt Priddis (16) and Andrew Gaff (16) quiet by their lofty standards.

Simpson said he would analyse every facet of the game to discover what the issues are. 

"Mental, fitness, personnel, we've got to look at everything," Simpson said.

"It's been happening long enough probably to become a pattern, or definitely. 

"They're the moments that you look forward to as a player and some players stood up and some didn't." 

West Coast sits in ninth spot with a 9-8 record and a percentage of 101.4. It hosts the Brisbane Lions next week before matches against St Kilda (Etihad Stadium) and Carlton (Domain Stadium).

The coach acknowledged his team had blown a crucial chance.

"It's the opportunity lost, isn't it? The season's so close and it shows you where Collingwood are at as well. They're still fighting for their season and everyone is, so you've got to be on all day," Simpson said.

"Your will to win, in the end, will win you some games. Unfortunately, we didn't match Collingwood in that area." 

Veteran Sam Mitchell is a likely in for next Sunday's clash but Simpson forecast a longer-term focus at the selection table. 

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"We need to keep exposing our kids when we can. Look at where we're at, for not just next week but for next year and what we need to do to get better. The players are aware of that," Simpson said. 

"Today was a big game obviously, there was a lot on the line. We let it slip. For three quarters we were pretty competitive and we thought we had our fair share of the play but that last quarter, not good enough." 

He left open the possibility of established players being relegated to the WAFL, with some changes perhaps needing to be made. 

"We'll have to have a look at it. There's obvious transitions we're making at the moment. We're exposing some of our kids to the big lights," Simpson said. 

"We'll look at that, we'll look at some of our senior players and see where it sits."