THE QUESTION is still being debated at St Kilda: Tall or small?

With the club forced to react to losing a trio of key players for various reasons ahead of Friday night's semi-final against reigning premier Richmond, Brett Ratten and the club's coaching staff is still working through what approach it will take in the backline.

Jake Carlisle will miss, having returned to Victoria for the birth of his child, while Paddy Ryder (hamstring) and Ben Long (suspension) are also unavailable for selection.

Josh Battle is likely to return following a foot injury, while Dylan Roberton is "very close" to earning selection after just five games in three seasons due to ongoing heart issues, but a complicated decision is still facing the Saints in regard to the team's defensive outlook.

St Kilda went on the small side earlier this season in a 15-point loss to West Coast and could recall Shane Savage and take a similar route against Richmond. But Battle, Roberton and potential forward inclusion Jon Marsh could give the Saints a taller team.

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Richmond coach Damien Hardwick said earlier this week that his side could look to stretch an undersized St Kilda, with Tom Lynch returning to partner Jack Riewoldt, Toby Nankervis and potentially Mabior Chol, with Ratten wary of just how to defend the taller Tigers.

"It's the talking point at match committee … do we roll the dice and go small in defence, or do we go with a bit more height and make sure that we can defend those players?" he said.

"The West Coast game, at times it was good but there was a patch in the second quarter which was horrible for us. It's been a talking point and we'll just wait and see on that."

St Kilda will make the three-hour bus trip from its hub in Noosa to Gold Coast on Thursday afternoon, giving the side as much preparation time as possible for the must-win semi-final.

It adds another complicating factor to a week where the Saints lost Ryder and Carlisle, before being unsuccessful in their attempts to free Long from a one-match suspension at the AFL Tribunal.

"There will be three inclusions, which is not perfect, but that's the way it is," Ratten said.

"We had a different-looking team from the first final to when we first played Richmond, when Marsh played and a few others as well. It might look a bit similar to that."

Ryder's absence will mean Marshall will have to ruck solo on Friday night. However, despite the pressures involved, Ratten backed the club's gun youngster to overcome dual premiership big man Nankervis.

"Last time it was Marshall against Nankervis and it was one ruckman each," Ratten said.

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"They might have two this time, by all reports. But I think Rowan has been ready to go and is looking to play more ruck time, so it's a great opportunity for him.

"That's why we brought Paddy in, to make sure they were fresh at the pointy end of the year. It's been a big workload for some of the rucks in the competition, who have had to do it by themselves. But he's ready to go. I think he'll really thrive in this environment."