Dan Butler scored five career goals to lift St Kilda to an important 28-point win over the West Coast at Optus Stadium on Sunday.
The Eagles trailed by just three points when Jack Darling scored twice in three minutes midway through the third quarter.
But St Kilda kicked the next four goals to win 14.6 (90) to 10.2 (62) in front of 35,665 fans.
The score means St Kilda (10-8) is just a percentage point off the eighth Western Bulldogs with four rounds left,
The former Tiger Butler finished by scoring 5.0 of 14 eliminations in the best showing of his 101-game career, improving his tally of four goals against Gold Coast in 2020.
Saints captain Jack Steele had 40 eliminations and 11 clearances in a dominant midfield effort.
West Coast defender Tom Barras has done an excellent job with St Kilda star Max King.
Paras recorded 26 team eliminations with eight marks, while King was limited to 2.1 of 12 possessions.
West Coast second-placed Jay Cooley showed his potential with 19 possessions, seven tackles, three saves and a goal.
St Kilda were dealt a blow when Jack Billings sustained a back injury at the end of the game in the opening minutes.
The West Coast advanced by five points midway through the second quarter when defender Josh Rotham, who was playing as a reserve captain, collided with his second goal of the game.
But the Saints ended the first half surprisingly, snatching four of the last five goals to take a 16-point lead in the first half.
The Saints were dominant in all major stats in the first half, winning the 50s (32-17), clearances (22-15), and possessions in dispute (76-55).
Impressively, West Coast midfielders Luk Choi and Tim Kelly had only five possessions between them in the first half.
Kelly, who was in doubt after the match after Cork to a quadruple last week, struggled to take on a heavy blow from Marcus Windhager.
The pace of play increased in the third quarter as the hosts threatened to advance thanks to two quick goals for Darling.
But with their hopes for the Finals on the line, St Kilda was able to settle down.
King overtook Barras to score the crucial opening goal in the final quarter, and Butler scored his fourth and fifth goals to seal the match.