Fremantle assistant coach Chris Scott says a team effort will be needed to shut down St Kilda's twin towers Nick Riewoldt and Justin Koschitzke in Sunday's clash between the two AFL sides at Subiaco Oval.

While Koschitzke has been in indifferent form of late, averaging just a goal and nine possessions in his past three matches, Riewoldt has been a shining light all season for the Saints.

The 25-year-old, who has bagged 44 goals this season, terrorised the Dockers in St Kilda's eight-point victory in round 13, tallying 25 possessions, 18 marks and three goals in a best afield performance.

Luke McPharlin, Antoni Grover, Michael Johnson and Steven Dodd are all in line to man either Riewoldt or Koschitzke but Scott said it would take more than two men to quell the star Saints duo.

"It's a team effort against those two, it's going to have to be," Scott said.

"How exactly that works I'm not prepared to go into.

"It's fair to say we won't expect one person to be doing the job on Riewoldt the whole game.

"You need to help out Riewoldt's direct opponent because it's too big a job for one guy.

"Koschitzke's under a little bit of pressure (due to a drop in form) but we know he's a top-line player when he's on his game."

Fremantle head coach Mark Harvey predicted the Saints, who are clinging to eighth spot with Brisbane and Carlton just a game further behind, would come out firing following two surprise losses in the past three weeks.

"St Kilda have copped a bit of criticism already this week and you always have got to be on guard and wary of that," Harvey said.

"Specifically players that have been mentioned in the media from St Kilda - they are the ones you have to be very careful of because they've got a lot of pride and they want to come out and prove everyone wrong."

St Kilda suffered a shock 17-point defeat to West Coast at Subiaco Oval in round 17 and Harvey said he would look at that game to determine why the Saints struggled at the longer venue.

"You go back and have a look at that game and see why (they played badly)," Harvey said.

"You don't try to emulate the way West Coast play but you look at different areas of where you can possibly find that weakness."

Fremantle have made two changes to the side that lost to Sydney last week, with Jeff Farmer and Grover replacing injured duo Chris Tarrant (shoulder) and Josh Carr (groin).

But with doubts still surrounding the availability of Brett Peake (shoulder) and Grover (personal reasons), a late change is on the cards.

Forward Ryan Murphy, midfielder Des Headland and 19-year-old Clayton Hinkley are Fremantle's three emergencies.

The Saints have also made two changes, with Charlie Gardiner and Raphael Clarke returning at the expense of the suspended Aaron Fiora and Jarryn Geary (omitted).

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