St Kilda's push to make just its second AFL grand final in 34 years has suffered a major setback, with stars Aaron Hamill and Justin Koschitzke ruled out for Friday night's preliminary final.

The absence of the injured marking forwards for the MCG clash with the Swans is a huge blow, given their combination with Fraser Gehrig and Nick Riewoldt would have posed a massive test for Sydney's defence.

Assistant coach Matt Rendell said Hamill was yet to recover from a calf injury sustained in the qualifying final win over Adelaide, while Koschitzke was still affected by the quadriceps injury suffered in round 21.

"Kosi won't make it, and Hamill won't play," Rendell told radio station SEN.

"We're very confident that both of them, if we happen to win this Friday night, will be able to get up for the following week, but they're not going to be quite ready this week."

While there was speculation the Saints were playing mind games - fuelled by the pair's participation in a supposedly secret light run at a Brighton Park, Sydney coach Paul Roos was prepared to take them at their word.

"One thing Grant (St Kilda coach Grant Thomas) doesn't do is play mind games," Roos said.

"I'd take it on face value, but ... really we just have to go about our business.

"We know their team is going to be very good regardless of who they put on the field.

"They've got some super players and they've probably got as much depth as any team in the competition.

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