Rockingham and Baldivis will fight it out for the minor premiership on Sunday at Anniversary Park.
The Rams and Brumbies both recorded wins on Sunday to leave them at the top of the Peel Football League ladder on 56-points.
Rockingham defeated Pinjarra by 30-points while Baldivis had a 22-point win over Centrals.
Waroona moved off the bottom of the ladder defeating South Mandurah by 41-points and Halls Head who have been relegated to bottom place on the ladder suffered a 113-point to Mandurah who received a major percentage boost.
Mandurah can now climb Centrals to fourth in the standings if the Mustangs defeat Waroona and Centrals lose to Pinjarra.
Halls Head and South Mandurah will play off for the wooden spoon.
LADDER: Rockingham 56 (224.35%), Baldivis (160.76%), Pinjarra 52 (140.50%), Centrals 36 (100.00%), Mandurah 32 (107.26%), Waroona 16, South Mandurah 12, Halls Head 12.
Round 18 Fixtures:
Centrals v Pinjarra 4:30PM Mundijong Oval
Rockingham v Baldivis 2:00PM Anniversary Park.
Waroona v Mandurah 2:30PM Parnell Street Oval.
Halls Head v South Mandurah 2:30PM Merlin Street Reserve.