Northern Districts will take a mental edge into their likely finals clash against Bomaderry following a 32-point win over the Tigers at Artie Smith Oval on Saturday.
Norths were outplayed well into the second quarter but were too strong in the end in an 11.7 (73) to 5.11 (41) win to seal third spot.
Bomaderry will finish fourth, with the two clubs to meet for a second consecutive season in the elimination final on August 23.
Norths coach Leigh Forsyth said it was an important win and would give his side confidence for their finals clash.
"Nobody at our club can seem to remember the last time we beat Bomo at Bomo," Forsyth said.
"They're remarkably resilient and play the game the right way. For a quarter and a half they outplayed us but we kicked a couple of late goals to hit the front at half-time.
"I said to the boys 'We've got back into it, now let's make a statement and go on with it' and we did.
"The last quarter was really pleasing and to beat them twice now and know our best footy can beat them gives us some confidence for the finals in three weeks."
Last season Norths also beat Bomaderry in the run-in to the finals only to be knocked out by the Tigers in the elimination semi.
"It shows we have a lot of preparation and homework still to do," Forsyth said.
"No disrespect to Nowra and Port Kembla - our opponents in the final two rounds - but from here on the preparation will be geared at Bomaderry and the finals."
Meanwhile, Wollongong regained top spot on percentage from Kiama after both clubs tuned up for their blockbuster final-round clash with thumping victories in round 16.
Ricky Neels booted five goals and Ben Griffin and Travis Lothian three each for Kiama in a 19.16 (130) to 6.11 (47) home victory over Shellharbour Suns.
The Suns have been the big improvers in 2014 and led at quarter-time before the Power booted 17 goals to three in the final three terms.
Wollongong outclassed Nowra, winning 16.21 (117) to 1.5 (11), while Albatross forfeited to Port Kembla.
In Saturday's round 17, Figtree host Bomaderry, Northern Districts are at home to Nowra, Wollongong host Port Kembla and Albatross welcome Kiama.
Ladder: Wollongong 24, Kiama 24; Northern Districts 22; Bomaderry 18; Shellharbour 14; Figtree 12; Port Kembla 8; Nowra 6; Albatross 0.