The race for the top-five will go down to the final round after Wollongong United and Albion Park White Eagles pulled off crucial wins over the weekend.
Both clubs needed the three points to keep their finals hopes alive and they delivered under pressure.
Park beat Tarrawanna 3-1 while United edged out Woonona 1-0.
It sets up an enthralling conclusion in the battle for top-five spots, with four clubs in the running for two spots.
Tarrawanna (35 points) currently lead Port Kembla (33 points), Wollongong United (33 points) and Albion Park White Eagles (31 points) on the competition ladder.
In a thrilling finale, Port Kembla will host the White Eagles in round 22 while United face off against the Blueys.
United coach Zivko Jovanovski was excited by the prospect of his side deciding their fate on the last day of the season.
“Our destiny is in our own hands now,” he said.
“It is better to have it this way than for it to come down to relying on other teams. It’s not down to anyone else but us but that’s the best way to have it.”
United gave themselves hope of a final berth with a gritty performance in difficult conditions at Ocean Park.
Zac Mclaren scored the game’s only five minutes before half time.
In other matches, Port Kembla missed the chance to sure up their top five position in a 0-0 draw with Cringila on Sunday.
Kemblawarra beat Picton Rangers 3-0.