WEST Coast has escaped from a nail-biting arm wrestle against Greater Western Sydney with arguably its most important victory for 2018, a gritty 11-point triumph at Optus Stadium on Sunday.

After three straight losses since the bye, the once high-flying Eagles were in freefall and looked in serious jeopardy of wasting their 10-1 start and coughing up a crucial top-four spot.

But in an epic finish to round 16, Adam Simpson's men held off the surging Giants, buying themselves some valuable breathing space in the run to finals with a 13.8 (86) to 10.15 (75) triumph.

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The victory sets up a massive encounter at the MCG next round, when the third-placed Eagles will face off with second-placed Collingwood, while 10th-placed GWS' season could be on the line in another blockbuster against Richmond. 

The Giants have dropped from sixth spot on the ladder following the loss in Perth and are half a game outside the top eight.

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After battling soreness all week and almost being rested, talismanic West Coast ruckman Nic Naitanui was relatively quiet in the opening half.

However, after copping criticism for not standing up when it mattered against Adelaide last round, the big man took two Mark of the Year contenders in an almost identical spot in the second half which noticeably lifted his teammates as they held on for an epic win. 

Sunday's clash wasn't without plenty of nervous and controversial moments in the dying stages.

From 23 points up into time-on of the third quarter, the Eagles watched as the rampaging Giants ate up the deficit with a stunning four-goal burst either side of the final break.

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Both sides' forward lines were decimated, and it was Adam Tomlinson (three goals) and Stephen Coniglio who inspired the visitors.

When star half-back Lachie Whitfield put GWS in front with a long-range major at the 11-minute mark of the final term, Leon Cameron's men had all the momentum.

Prolific Eagle Andrew Gaff's (41 disposals, two goals) brilliant snap wrestled back the lead, but only momentarily before Harry Himmelberg was awarded a holding the ball free kick against Tom Cole from 20m out directly in front of goal, which incensed the 52,105-strong crowd.

But, fittingly in a week when Hawthorn superstar Cyril Rioli announced his shock retirement, it was some magic from cousin Willie which secured a famous West Coast win.

Rioli's mark and long-range set shot handed Simpson's side a seven-point lead, and when Jeremy McGovern (two goals) took advantage from a free kick moments later the Eagles had done enough.

"It would've been a pretty good spectacle. Both teams had a real go. Momentum shifted throughout the game, a real arm wrestle and to get over the line we're really proud of our players," Simpson said post-match.

"We just hung in there and we, sometimes, couldn't keep up with our own ball movement, which exposed us the other way, and I think the Giants had the same issues at stages, so it would've been a bit of a 'ping pongy' game there.

"But in the end we found a way to get over the line."

At 11-4, the Eagles are a win clear of fifth-placed Sydney and will cross their fingers at least one of star forwards Josh Kennedy or Jack Darling will be back from injury next round.

The Giants were missing twin towers Jeremy Cameron (suspended) and Jon Patton (ACL), plus gun small Toby Greene.

In their absence, Tomlinson and Himmelberg combined for five majors, while Coniglio (30 disposals, one goal) did everything in his power to lift the visitors.

Gaff was simply superb for the Eagles, while Elliot Yeo (32, four clearances) relished a move back to midfield, Luke Shuey (32) extracted 12 clearances and skipper Shannon Hurn (24 disposals) saved the Eagles on numerous occasions.

Mark Hutchings performed an excellent shutdown job on Josh Kelly (26 disposals) and hit the scoreboard with two majors by half-time as the Eagles edged out to a 13-point buffer at the long break.  

That margin proved decisive, and Giants coach Leon Cameron lamented his side's inability to win the big moments when it counted late on Sunday.

"It was disappointing ... we were right in it and we poked our noses in front," he said.

"But it seemed like, other than the first quarter, we were always trying to make up a goal or two. And, in the end, that's the difference, 11 points.  

"It's disappointing that in the big moments, especially halfway through the last quarter onwards, they just had some better moments than we did (and) they made better decisions."  

West Coast: Naitanui got up sore after landing heavily from his first Mark of the Year contender but played on and the Eagles seemed to get through unscathed. 

Greater Western Sydney: The Giants appeared to come out of the game without any major injury concerns, although Harry Perryman came off with hamstring tightness in the final term.

The Eagles face a daunting challenge travelling to the MCG to take on rampant Collingwood, while it is almost do-or-die time for Greater Western Sydney against runaway League leader Richmond back at Spotless Stadium.

WEST COAST                                  1.2   6.3   10.3  13.8 (86) 
GREATER WESTERN SYDNEY        2.2   3.8  7.12   10.15 (75)  

West Coast: Rioli 2, Hutchings 2, Cripps 2, Gaff 2, McGovern 2, Lycett, Ainsworth, Redden  
Greater Western Sydney: Tomlinson 3, Himmelberg 2, Whitfield, Ward, Perryman, Coniglio, de Boer,  

West Coast: Gaff, Yeo, Hurn, Redden, Hutchings, Shuey, Naitanui
Greater Western Sydney: Coniglio, Whitfield, Tomlinson, Taranto, Himmelberg, Ward 

West Coast: Nil     
Greater Western SydneyNil

Reports: Nil 

Umpires: Meredith, Findlay, Gianfagna 

Official crowd: 52,105 at Optus Stadium