The Falcons have not finished lower than fifth since finishing seventh in 2004.
A win against the Tigers at Claremont Showground on Saturday will return the reigning premiers to fifth spot on percentage.
A final-round triumph over last-placed Perth would seal the position.
A loss to Claremont would make it only the third time in the last 22 years the club has not been amongst the league’s best five at season’s end.
It has been rare for West Perth to finish lower than fifth after a horror run of three-straight wooden spoons from 1990 to 1992.
Seasons 1997 (sixth) and 2004 stand as the only years it has happened since.
The Falcons were in an arm wrestle with Fremantle-affiliate Peel in Mandurah on Saturday before toughing out a 9.14 (68) to 8.11 (59) victory.
Scores were all tied up at half-time, with the home side taking an eight-point lead early in the third quarter.
But the visitors kicked the next four goals, youngster Luke Meadows booting two of them to give him a match-high three goals in just his fifth game for the side.
The Thunder got back within three points early in the final term after being 10 points down at the break. West Perth responded to the challenge with the next six scores (1.5) to win by nine points.
The Falcons’ Aaron Black and Rohan Kerr took an equal match-high 32 disposals.
Debutant Ben King had 10 touches and three marks.