WEST Coast's defenders will back their ability to mix and match opponents in Saturday night's knockout semi-final against Carlton, with the Blues' fleet of small forwards looming as a key to an upset victory.

Livewire goalkickers Eddie Betts, Jeff Garlett and Andrew Walker have all kicked more than 45 goals this season and they combined for 10 goals in their team's 62-point demolition of Essendon last Sunday.

However, at Patersons Stadium, they will encounter an in-form Eagles backline led by captain Darren Glass and boasting up to five other lockdown options for the dangerous Carlton trio. 

Defender Sam Butler said the Eagles' back six had gained confidence all season from their ability to play on a variety of opponents and they would use that to their advantage on Saturday night.

"We feel pretty confident swapping, and we generally don't say we have to lock in on one player - one backman for one forward," he said. "We switch up a bit and share the load, so we'll be confident.

"Their small forwards are very dangerous [but] we've got players like [Patrick] McGinnity, Beau Waters, myself, Shannon Hurn and Adam Selwood that all play on those kinds of players.

"We can mix and match a bit and hopefully shut them down."

West Coast held Carlton to its third-lowest score for the season, 10.7 (67), when the teams met in round 14, winning by 26 points, with Walker - who leads Carlton with 53 goals this season - kept goalless.

Butler said the back six would draw confidence from their individual performances against the Blues that day, but it was the team's defensive efforts up the ground that had proved crucial all year.

"If we can shut them down in our press then all better for the back line because the ball doesn't come down there at all," he said. "That's our first focus, we want to shut it down and keep the ball inside our 50m arc."

Half-back Hurn, who has played every game this season, agreed that the Eagles' versatility in defence had been a key to the team's success this year, with the back six entering Saturday night's final at close to full strength. 

Third-year defender Ash Smith has been a valuable addition to the defence in 18 games this season, but he faces a battle to regain his spot after suffering a hamstring injury, highlighting the competition for spots.

"I certainly feel we're at about full strength, and there's a bit of depth there," Hurn said of the backline, which has been led this year by assistant coach David Teague.

"Having senior players down there that have all played over 100 games is very good, but I feel just as comfortable alongside Ash Smith, who's come along really well.

"We've worked really hard together and we understand what we're trying to do and we're carrying that out in games.
 
"We're playing confident footy and I think that shows."

Nathan Schmook covers West Coast news for afl.com.au. Follow him on Twitter: @AFL_NSchmook

The views in this article are those of the author and not necessarily those of the AFL or its clubs