WEST Coast captain Darren Glass has backed teammate Eric Mackenzie to bounce back from a horror last quarter against St Kilda, with a possible match-up against Fremantle skipper Matthew Pavlich looming in Sunday's Western Derby.

Mackenzie was superb in the Eagles' backline for the majority of Saturday night’s clash with the Saints, holding star forward Nick Riewoldt goalless, but let himself down with a pair of crucial clangers that led to two goals and helped St Kilda secure victory by 21 points.

Glass, who said Mackenzie's improvement this year had allowed him to spend less time on the opposition's best forwards, said his younger teammate would move on quickly from the costly mistakes.
 
"Eric's a terrific player, and I've told him time and time again that he's well and truly advanced on where I was at that age," Glass said from Patersons Stadium on Monday. 

"To hold Nick Riewoldt to one scoring shot, or one point, is a big effort.

"He played a great game, (but) down back mistakes are magnified. You can do a simple spoil down back and it can look great or you can mess up a kick and it can look poor.

"I know he does a lot of work on his kicking, and he'll be fine. You have to move on pretty quick and he's probably got another big challenge this week."

Stopping Pavlich, who has kicked 13 goals and averaged more than 22 possessions in his last five games, will be a key for West Coast on Sunday as it looks to notch consecutive Derby wins for the first time since rounds three and 20, 2005.

Glass, who could play on Pavlich if the Fremantle skipper lines up deep in attack, said Mackenzie would spend periods on the six-time All Australian, with athletic defender Will Schofield providing another option.

The Eagles will also be monitoring Daniel Kerr's fitness this week after the rejuvenated midfielder missed Sunday's loss with hip and glute soreness. Glass said the 28-year-old was a chance to line up in the Derby.

"It was disappointing to miss him last week and I think we did miss his drive through the midfield," Glass said of Kerr.

"Hopefully he'll be back."

West Coast will enter Sunday's Derby just one game and percentage ahead of sixth-placed Fremantle, and Glass remained wary of the Eagles’ cross-town rival, which has defied injury to win four of its last five games. 

The skipper said it was a big game for his fifth-placed team as the players look to continue their charge at the top four.

"I think it's a big game for us because we want to finish as high on the ladder as we can," Glass said.

"We want to keep pushing for a top four spot and then if we can push another challenger down, that's all the better."

Vice-captain Beau Waters pulled up well from his first game since round two, Glass said, while the form of No.4 draft pick Andrew Gaff, who had 21 disposals and kicked two goals in his return to the team, pleased the skipper.

"He was in outstanding form with South Fremantle," Glass said.

"Great kid, great character, and it was good to see him play well.

"I'm sure he'll be in the side for, hopefully, the rest of the year."

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