Brent Prismall's likely knee reconstruction was the one disappointment for Geelong as they blew St Kilda away in their AFL qualifying final.

Saints legend Robert Harvey also had some angry words with Matthew Scarlett immediately after the final siren, but otherwise the 17.17 (119) to 8.13 (61) demolition generally went to script.

Like Hawthorn's dispatch of the Western Bulldogs on Friday night, the only aspect of the game where the reigning premiers let themselves down was goalkicking.

The Cats corrected that problem with 9.5 to 2.3 in the third term and they now have the week off before the preliminary final against either the Western Bulldogs or Sydney.

St Kilda have six days to regroup ahead of Saturday night's semi-final against Collingwood.

Prismall, 22, was playing his sixth senior game this season and was chasing the ball midway through the first term when his right knee collapsed.

The Cats will probably confirm on Monday that he will need a reconstruction, sidelining him until late next season.

They have several ready-made replacements, including James Kelly and David Wojcinski, but coach Mark Thompson did not want to forget about Prismall just yet.

"We were pleased he was in our best team coming into the finals and it was up to him whether he stayed there," Thompson said.

"He's a terrific kid. It's a bit of a tragedy, really.

"It's really sad that he got injured and to say that we've got ready-made replacements shows a bit of disrespect for 'Pris', I think."

Paul Chapman spent the second half on the bench and walked off with ice packs on a hamstring and a quad, but the Cats think he will be fit for the preliminary final.

It is unknown what prompted the Harvey-Scarlett spat immediately after the final siren.

There was certainly some feeling between the two teams during the game and St Kilda onballer Lenny Hayes was booked for striking Joel Selwood.

Saint small forward Stephen Milne also gave away a "double goal" in the third term when he bumped Steve Johnson immediately after Brad Ottens had kicked truly.

The Cats had winners everywhere, with Jimmy Bartel best afield, Gary Ablett again dynamic, Ottens superb in the ruck and their defence typically rock-solid.

Young backman Harry Taylor beat Saints captain Nick Riewoldt in a surprise match-up.

"We sort of went wide with our entries (early) and we were trying to score goals from outside, which is in anyone's terms, it's hard to score from out there," Thompson said.

"But the fundamentals were right and certainly by the third quarter, we were pretty fantastic."

Saints coach Ross Lyon was left lamenting a disastrous afternoon, where very little went right.

The Saints tried to take it up to the Cats and not play too defensively, but after a solid start they were no match for the AFL's top team.

"They won the contested ball, they used it really well, we struggled to slow them in their ball movement," he said.

"Their midfield got on top and we couldn't get hands on the footy.

"If you're not (good in those areas), you'll get steamrolled.

"I thought the scoreline flattered us."

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