St George Illawarra Dragons and Cronulla Sharks made the most of top-four rivals Penrith Panthers going down at home to Newcastle Knights in a match that saw four players sin-binned for fighting.
Just 22 men remained on the pitch at the final buzzer as the Panthers lost their grip on fourth place in the NRL amid chaotic scenes, the Dragons leapfrogging them and the Sharks moving level with both on 30 points after respective victories over Wests Tigers and North Queensland Cowboys.
Aidan Guerra and Cory Denniss got the Knights off to a strong start, with Sione Mata'utia keeping them on top after Tyrone May crossed.
Things boiled over following Ken Sio's score, with punches being thrown in the final five minutes as Penrith duo May and Viliame Kikau and Newcastle pair Danny Levi and Shaun Kenny-Dowall were shown yellow cards.
May and Kikau's actions could put their availability for the Panthers' crunch trips to New Zealand Warriors and Melbourne Storm in doubt.
Jordan Pereira, Luciano Leilua and Tyson Frizell all crossed for the Dragons in a 20-10 victory over Wests Tigers, whose hopes of making the Finals are now all but over.
Paul McGregor's team ended a run of three straight defeats despite the injury-enforced absence of star half-back Gareth Widdop and face teams with nothing to play for – Newcastle and Canterbury Bulldogs – in their two remaining fixtures.
Cronulla ran in five tries to remain in the hunt for a top-four spot with a 28-16 win over the Cowboys in Queensland Maroons icon Johnathan Thurston's final match in Sydney before retirement.
Late efforts from Josh Dugan and Jayson Bukuya finally got the Sharks clear of a resilient North Queensland side, who will hope to see Thurston off with a win in his last home outing against Parramatta Eels on Friday.
