Collingwood will limp into a sudden-death AFL final against Adelaide next weekend without star onballer Scott Pendlebury and veteran forward Anthony Rocca - both of whom have suffered likely season-ending injuries.

Magpies coach Mick Malthouse said Pendlebury had a suspected broken leg and Rocca had re-injured his troublesome ankle, adding an even gloomier post-script to their 28-point qualifying final loss to St Kilda at the MCG on Sunday.

Pendlebury was badly injured inside the first few minutes of the match after a Saints opponent fell heavily on his leg.

He bravely returned to the field heavily strapped but was unable to keep going beyond the second quarter.

Pendlebury is set to have scans on Monday on what the club's medical staff believe is a broken fibula.

Rocca, in just his fourth game this season, injured the ankle he had surgery on earlier this year late in the Pies' 12.8 (80) to 7.10 (52) loss to the Saints and will also have scans.

Collingwood coach Mick Malthouse now has six days to repair and re-focus his side - most notably some of the Pies' stars who went missing in action against the Saints.

While Collingwood's quality midfielders Alan Didak, Dane Swan and Leon Davis were down and Pendlebury out, the Saints scored maximum return from their match-winners to put a swagger in their September step.

Skipper Nick Riewoldt led the way with an inspirational five-goal haul, midfield guns Lenny Hayes and Nick Dal Santo dominated and defender Sam Fisher picked up 42 touches running loose across half-back.

The Saints are now just one win from making the grand final, and have earned a weekend off ahead of the preliminary final in a fortnight's time.

Malthouse admitted his side had been comprehensively beaten in the midfield, but was confident there was enough quality and hunger among his players to re-right a season on the brink.

"That's the art of showing some courage and getting back," Malthouse said.

"You want to recover, you want to get back into it. We have got and have earned the right to play another game.

"We have got a very good record of tight, close duels against Adelaide.

"I wouldn't have thought because you lose a game you turn your toes up. That would be a total indictment of the quality of the person and the club."

St Kilda controlled the match from late in the second quarter, as Riewoldt booted three goals in the term including one on the halftime siren to give his side a 10-point lead.

Despite their midfield dominance, the Saints still spent most of the second half trying to shake a Collingwood side rarely able to get their hands on the football - the Saints taking just a 17-point lead to the final change.

It was Riewoldt's interjection at crucial times - none better than a sensational right-footed goal on the run early in the fourth term to give his side a 29-point lead - that swayed the match.

As well as his five goals, Riewoldt grabbed 19 touches, 10 marks and five tackles as he combed the field tirelessly, especially when the game was there to be won.

Magpies skipper Nick Maxwell and defender Heath Shaw were their side's best.

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