The Cats kicked 18.15 (123) to 11.15 (81) to all but end the Saints' hopes of playing in a fifth consecutive finals series.
Geelong was dominant in the first half without the scoreboard truly reflecting the one-sided nature of the contest.
James Kelly was one of his team's best with his tireless efforts, finishing with 27 possessions, while Mitch Duncan continued to build his reputation as a key part of the Cats line-up.
Tom Hawkins seemed ready to single-handedly tear the Saints apart, exploiting their lack of size in defence and beating James Gwilt on the lead to have four first-half goals and finish with six for the night.
St Kilda could not penetrate a rigid Geelong defence in the first half with Andrew Mackie and Corey Enright rebounding solidly, while Harry Taylor cut off numerous St Kilda thrusts.
With a 34-point lead at the main change, the Cats looked set for an easy win, but the tide changed after the two sides returned.
St Kilda had 10 scoring shots in the third quarter but only three of them were majors while the Cats were held goalless for a quarter for the first time this season.
The spark for the Saints seemed to come with the substitution of Justin Koschitzke. The tall forward did not have a possession in the first half and managed just one handball in the third quarter before he was given the red vest.
Shortly after, the luckless Rhys Stanley suffered his third injury of the season and was taken to hospital with broken ribs in his first game back from a hamstring injury.
Suddenly, the St Kilda forward line without Koschitzke and the injured Nick Riewoldt looked a lot more nimble and unpredictable, and the Cats' back six struggled to adapt to the Saints' change of pace.
Stephen Milne, kept goalless in his previous two matches against Geelong, was the danger man, booting four goals while Ahmed Saad was just as explosive.
The Saints kicked the first two goals of the final term to bring the lead back to just one point but the Cats, spurred on by a tongue-lashing from coach Chris Scott at the three-quarter time break, sprung into action to boot the next seven and run away relatively easy winners.
GEELONG 5.3 11.9 11.13 18.15 (123)
ST KILDA 3.2 6.5 9.12 11.15 (81)
GOALS
Geelong: Hawkins 6, T Hunt 2, West 2, Motlop 2, Podsiadly 2, Stokes, Murdoch, Mackie, Chapman
St Kilda: Milne 4, Saad 3, Geary, Armitage, Goddard, Schneider
BEST
Geelong: Kelly, Duncan, Hawkins, Johnson, West, Taylor, J Hunt, Murdoch
St Kilda: Gram, Montagna, Hayes, Milne, Armitage, McEvoy, Saad, Dempster
INJURIES
Geelong: T. Hunt (broken nose)
St Kilda: Blake (ankle) replaced in the selected side by Stanley; McEvoy (broken nose), Stanley (ribs)
SUBSTITUTES
Geelong: Jonathan Simpkin replaced Joel Corey at three-quarter time
St Kilda: Adam Schneider replaced Justin Koschitzke during the third quarter
Reports: Nil
Umpires: Donlon, Rosebury, Meredith
Official crowd: 38,169 at Etihad Stadium
The views in this article are those of the author and not necessarily those of the AFL or its clubs
