After a dismal start to the season, the Eagles had breathed life into their campaign by winning four straight games to thrust themselves firmly into the finals conversation.
However, after suffering a shock four-point loss to Port Adelaide last round, West Coast (4-6) knew they needed a victory at Sullivan Logistics Stadium on Saturday to be a realistic chance of a top-eight finish.
But an 8.18 (66) to 1.7 (13) defeat against the high-flying Cats (9-1) means they sit four points adrift with a much lower percentage than eighth-placed Adelaide with two rounds remaining.
On the other hand, Geelong have strengthened their grip on a top-two finish and have returned to the summit of the ladder, although they will need reigning premiers North Melbourne to lose to the 17th-placed Bombers on Sunday to finish on top at the end of the round.
The Cats' ninth straight win came off the back of Prespakis's 39 disposals, six tackles and six clearances as she continues to push her case for the competition's best-and-fairest award.
Fellow midfielders Mikayla Bowen (27 disposals, nine tackles) and Nina Morrison (27 disposals, one goal) were also inspirational, although the Cats may have to sweat on the fitness of forward Jacqueline Perry, who left the field early with an injury.
Geelong dominated from the second quarter onwards and held West Coast goalless until late in the final term, although defender Charlotte Thomas had 26 disposals.
Elsewhere, Brisbane ended their five-game losing streak by dealing a hammering to Port Adelaide's final hopes in a 5.4 (34) to 2.6 (18) victory at Brighton Home Arena.
With top-eight contention all but ruled out for the Lions, last year's grand finalists were superb in defence, holding their opponents to just one goal in the first half and winning the clearance count 24 to 20.
The result means the Power (4-6) remain one win behind the Crows (5-5), who also boast a significantly higher for-and-against.
Ruck Matilda Scholz was typically busy for the visitors, registering 22 disposals, 24 hitouts and a goal, while midfielder Abbey Dowrick posted a game-high 28 possessions and seven clearances.
For Brisbane, Alexandra Anderson shone with 24 disposals, while midfielder Isabel Dawes recorded 16 disposals, four clearances and a goal.
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