COLLINGWOOD coach Mick Malthouse will plan for every possible St Kilda line-up ahead of Saturday night’s semi-final, with injured midfielder Luke Ball and ruckman Michael Gardiner central to his calculations.

Ball hasn't played since he tore a hamstring in round 18 and has been rated an unlikely starter by the Saints. Gardiner hasn't played senior football since round 17 but put in a strong performance for the club’s VFL affiliate Casey Scorpions on the weekend.

Malthouse said the Pies will plan for every possible Saint selection as both clubs aim to be one of the last four standing come the final siren at the MCG on Saturday.

"You've got to plan for any player to play,” he said at the Lexus Centre on Wednesday.

“You look at their list and you look at the 22 that played last week, you look at players that are out and have had some impact on the season, and [Ball] has had a massive impact on their season.

"We'd be fools if we thought he wasn't going to play, and then all of a sudden be surprised if he runs up the race.

"You can't afford to be surprised in team selection. You might be surprised a little bit in team positioning, but not in selection. It's an indictment if you don't cater for it.

"They'll look at who they're playing and pick a side accordingly."

However, he did admit an inclusion of out-of-favour forward Fraser Gehrig might cause a few raised eyebrows in the Collingwood coach's box.

"That's one that might surprise me a little bit, but having said his name, I've still got him over in that column that could go to full forward," he said.

"I don't think he'd be playing too far up the ground, but you could still look at full forward, forward pocket."

Malthouse said the Magpies will not only look at their round-19 defeat of the Saints this week; they'll go back further in an attempt to identify specific trends that have evolved in their head-to-heads over the past year.

"I think we've been pretty competitive and I think they've all been close games," he said.

"I don't think we can get too over enthusiastic about it, but on the same token, we can take some confidence that we have played pretty well against them.

"We do know they've got some very talented footballers, and if you don't acknowledge that, you end up out of the finals race."

St Kilda coach Ross Lyon declared his side underdogs on Sunday after they were smashed by minor premier Geelong, but Malthouse refused to read into the comment and said the favourite status "won't give us a head start".

"What does it mean? Who makes them underdogs? The coach saying that or the media or the bookmakers? Does it really matter?" he said.

"I'm (constantly) astounded in sport; there's no solution to it. I'm one of many who have scratched their heads and thought why through every sport in the world, someone gets a hiding or beaten the previous week, (then) they find something special the following week.

"You've got to look back – they whopped Essendon, they beat Adelaide, and the one before that was Fremantle. Good form.

"Whether they're underdogs or not, it's really meaningless."