The Saints took full advantage of an injury-riddled but uninspired Richmond to give their percentage a huge boost with a resounding 27.12 (174) to 10.11 (71) win.
The result means the Saints have now beaten the Tigers by an average of 10 goals in their past seven meetings.
The win - the highlight of which was a season's best 10 goals from spearhead Fraser Gehrig - was enough to see Grant Thomas's team move back into the top four as its odds of securing the double chance shorten by the week.
But for the Tigers an already dreadful day was capped off by a hamstring injury to Nathan Brown while veteran Greg Stafford could come under scrutiny for a bone-jarring clash that forced Brendon Goddard to be carried off on a stretcher in the second term.
The Saints have now won their past five games since their much-publicised trip to the Victorian country town of Bonnie Doon and it seems "the serenity" of the town made famous in the Australian movie "The Castle" has done wonders for their morale and confidence.
After being fortunate to beat Essendon and Port Adelaide in the past two weeks, the Saints got back to the form that saw them demolish Hawthorn and Collingwood in the fortnight immediately after their trip to the bush.
After an even first 20 minutes the game was as one-sided as you could wish to see and the Saints have probably been under more pressure in some of their training sessions than they were against a rapidly-fading Richmond on Saturday.
The Tigers were rocked by the late withdrawals of experienced defenders Darren Gaspar (knee) and Andrew Kellaway (hamstring) as well as Andrew Krakouer (finger) with the trio replaced by Ray Hall, Stafford and veteran Mark Chaffey, who came in for his first game of the season following groin problems.
With their defensive options limited, Hall was forced to stand Gehrig while Joel Bowden gave away height to Nick Riewoldt.
While Bowden tried hard on Riewoldt, Gehrig was merciless on Hall and by half-time had already helped himself to seven goals.
The man known as "The G-Train" was back to his Coleman Medal-winning best in a performance which augers well for the Saints' chances come September.
What was even more impressive was his kicking for goal as Gehrig, who became the first player to kick 10 goals or more in an AFL game this year, did not produce a single miss until he had bought up his 10th goal.
Gehrig's devastating kicking spread to the entire team as the Saints amassed an incredible 23.1 between the first and last terms until Gehrig produced his first miss of the day.
But this was by no means just the Gehrig show with Leigh Montagna continuing his fine season with a devastating display while the underrated Jason Gram set up the game for the Saints with three first-quarter goals, off a half-back flank.
Gram ended the game with four goals - the same tally as he had kicked in his 25 previous matches.
While the Saints were magnificent and can look forward to their third successive finals campaign with confidence, yet again the Tigers are ending a season in inglorious fashion.
With three straight losses the Tigers now look certain to be September spectators yet again - they have made the finals just twice since 1982 - and it was the drop off in their skill level that must be of greatest concern to coach Terry Wallace.
The Tigers continually gift-wrapped goals for the Saints through poor skill errors with one of the worst coming just before half-time when David Rodan kicked into the man on the mark when attacking down the wing, allowing the ball to be immediately transferred to the other wing where Montagna goaled unopposed.
Unfortunately that one piece of play summed up the Tigers' entire performance.
Grant Thomas was suitably impressed by the efforts of his charges after the match and didn't hesitate when asked what he thought the most pleasing aspect of the win was.
"I think the consistency of the four-quarter effort where we continued to attack and probably the most pleasing thing from a coaching perspective, we all agreed, was the fact that we stuck to our plans and worked together as a team," he said.
"We stuck to our structures and we didn't collapse those sorts of things when the game was no longer in the balance which I think we've been guilty of in the past."
"You get a bit greedy and a bit selfish which teams can do, but we were really pleased with our selflessness and our team effort."
Richmond coach Terry Wallace said the loss - the club's third by more than 100 points this season - was similar to the round seven clash against Sydney when the Tigers capitulated after losing key defenders to injury just before the game.
And he said his side has to learn to become mentally tougher to be able to deal with such situations.
"In two of the games (the 100-point plus defeats) there has been a real similarity in that we lost players late in the week but not only did we lose those players but we lost the other players as well in that they have allowed that (the late withdrawals) to impact on their psyche leading in to the game," Wallace said.
"It was disappointing to lose Gaspar and Kellaway late in the week but they (the rest of the team) should still be going in with the right attitude and the right psychological approach."
"It's in those circumstances that mental strength arises and they have just got to handle those situations better."
ST KILDA: 5.5, 14.6, 23.6, 27.12 (174)
RICHMOND: 2.2, 6.7, 8.9, 10.11 (71)
GOALS - St Kilda: Gehrig 10, Gram 4, Montagna 3, Goddard 2, Riewoldt 2, Dal Santo, Ackland, Milne, Voss, Fiora, Harvey
Richmond: Richardson 4, Schulz 2, Tivendale 2, Johnson, Tambling
BEST - St Kilda: Gehrig, Gram, Montagna, Ball, Powell, Goddard, S Fisher, Harvey, Voss
Richmond: Raines, Johnson, Chaffey, Richardson, Deledio,
INJURIES - St Kilda: Hudghton (knee strain)
Richmond: Brown (hamstring)
CHANGES - Richmond: Gaspar (knee) replaced in selected side by Hall, Kellaway (hamstring) replaced in selected side by Stafford, Krakouer (finger) replaced in selected side by Chaffey
REPORTS - Nil
UMPIRES - Vozzo, Rosebury, Allen
CROWD - 43,250 at the MCG
