The Swans, who have a bye week to end the home and away season, defeated the Tigers by 11 points at Bassendean Oval on Saturday.
The 9.14 (68) to 7.15 (57) win positioned them four points clear of the Tigers, who can jump them for fifth spot with a win because of a healthier percentage.
n Any hope South Fremantle had of playing finals was lost following a 23-point defeat to West Perth at Fremantle Oval on Saturday.
The Bulldogs were right in the clash at the final change but could not keep pace with the second-placed Falcons, who booted four in the fourth term to win 12.13 (85) to 9.8 (62).
Bulldogs captain Ryan Cook kicked two goals for the Bulldogs to add to his haul of 25 disposals.
Ashton Hams had 39 disposals and kicked one goal. His brother Kyle gathered 32 disposals.
Matthew Fowler booted six goals for the Falcons.
Teammate Aaron Black had 33 disposals and Trent Manzone 29.
n Subiaco powered to their 16th win of the season by downing East Fremantle by 77 points at Leederville Oval.
Matthew Boland booted four goals for the minor premiers, with Lions teammate Kyal Horsley finishing with 27 disposals and one goal in the 16.17 (113) to 5.6 (36) win.
Brock O�Brien booted two for the Sharks, with Ryan Lester-Smith and Jamie McNamara tallying 22 disposals each.
Peel Thunder bounced back from a slow start to beat the WAFL�s lowest-ranked team Perth at Lathlain Park.
Gerald Ugle booted three goals for the Thunder and Jacob Ballard added two goals to his 34 disposals.
Perth�s Todd Stevenson booted four goals and Aidan Tropiano gathered 35 disposals in the 14.16 (100) to 13.9 (87) loss.