Souths' come-from-behind win lifted them two points clear of the Roosters who lost 30-22 to Gold Coast on Sunday. Friday's meeting at ANZ Stadium will still decide the minor premiership because the Roosters have a superior points differential and will win the regular season title if they beat Souths and the teams end level on championship points.
Manly winger David Williams scored a first-half hat trick as the Sea Eagles beat Melbourne 28-8 on Saturday - their first win this season over a top-four side - to leapfrog the Storm into third place. Manly had to beat Melbourne by 11 points to rise above them on the table and did so, running all six of their tries through the Storm's week left side defense.
The margin would have been greater had Manly captain Jamie Lyon not missed five of seven shots at goal.
"It was a gutsy performance, particularly after losing Jamie Buhrer in the first minute," said Manly coach Geoff Toovey. "We had to shuffle players around, but the first half was definitely our best half of football this year."
The Bulldogs moved into fifth place with a 34-14 win over Penrith and Cronulla stayed sixth after a 31-18 loss to North Queensland.
Penrith started strongly and scored two early tries against a Bulldogs team plagued by errors. But Tony Williams set up a try for Tim Lafai which turned the tide just before halftime and the Bulldogs ran away with the match in the second spell.
"They are a good side Penrith but we contributed to our downfall," Bulldogs coach Des Hasler said. "It's just not good enough and we need to improve.
"But luckily we tackled well and they were as guilty as were by completing just two sets more than we did. We improved in the second half and had some momentum and scored four tries."
Newcastle held seventh place with a 26-18 win over Brisbane, snuffing out the Broncos' finals hopes, while the New Zealand Warriors moved briefly into the top eight with a 50-16 win over troubled Canberra. They were subsequently displaced by North Queensland who won their fifth-straight match and now only have to beat Wests next weekend to claim the last finals place.