Cronulla has gone a long way to dispelling doubts about its ability to perform against the better sides in the NRL, taking down South Sydney 26-16 in Perth.

The Sharks shored up their spot in the top eight with the victory, jumping from eighth to fifth, just one win outside the top four, although the Raiders could move back ahead of them with a win over the Tigers on Sunday.

The Rabbitohs, meanwhile, have slipped from their status as premiership contenders to at risk of dropping out of the finals.

Souths' defeat was compounded by the loss of State of Origin prop Jai Arrow, who reeled out of a tackle in the second half suffering severe back spasms.

Cronulla have fielded criticism all season for failing to match it with the NRL's heavyweights — prior to Saturday, they had won only one of eight matches with sides that began this weekend in the top eight.

But just as the trend threatened to bring their finals tilt undone, the Sharks rediscovered their clinical best in attack to halt a three-game losing streak and surge to fifth on the ladder.

After welcoming star fullback Latrell Mitchell back from his long-term calf injury last week, the Rabbitohs had reason for optimism as the finals approached.

Against Cronulla, though, their attack did not click into gear until the final 20 minutes, when they scored three tries in 10 minutes and threatened to pull off an almighty comeback.

Souths prop Thomas Burgess went to the sin bin for the final four minutes of the game for making shoulder contact to Tom Hazelton's head, stifling all late momentum and allowing Cronulla to hold on.

When the game was there for the taking, Mitchell struggled for chemistry with rookie Tyrone Munro on the right wing so Souths could not exploit Cronulla's leaky left-edge defence — their major flaw in recent times.

No Reynolds, no problem as Broncos roll over Cowboys

Brisbane are on track for a top-two NRL finish after defeating rivals North Queensland 30-14 in Townsville behind an exemplary defensive display.

The Broncos held their nerve in a ferocious, end-to-end classic in which their try-line seemed at times to be impenetrable.

Five-eighth Ezra Mam stood tall without skipper Adam Reynolds (groin) in the halves, making numerous last-ditch tackles and even an intercept on his own line.

Dual wrecking-balls Payne Haas and Patrick Carrigan punched their way through the middle and laid the platform for fullback Reece Walsh to terrify the Cowboys either side of the ruck.

A try to Walsh with seven minutes remaining seemed to put the result beyond doubt before Heilum Luki crossed on his NRL return for the Cowboys to fuel the hopes of a sell-out home crowd.

But in a breathless finish, Selwyn Cobbo intercepted a pass a minute from time to cap off a thrilling win.

Without Reynolds pulling the strings for Brisbane, coach Kevin Walters will be pleased with just how compact the Broncos' defence was.

North Queensland had 38 play-the-balls inside Brisbane's 20-metre line but only came up with three tries.

Knights finish strong to beat Dolphins after Isaako's first-half hat-trick

The Newcastle Knights have soared into the top eight for the first time since round six after overcoming Jamayne Isaako's first-half hat-trick to post a 30-28 win over the Dolphins in Perth.

Isaako scored tries in the 23rd, 26th, and 31st minutes as the Dolphins shot out to a 14-6 lead in Saturday's NRL clash at Optus Stadium.

The Dolphins still led 20-12 early in the second half, but Knights fullback Kalyn Ponga starred from that point on to give his side a 30-22 lead with eight minutes remaining.

There was late drama in the match after Dolphins second rower Connelly Lemuelu crossed in the 73rd minute to reduce the margin to two points.

With just over three minutes remaining, the Dolphins had a scrum just metres from the Knights' line — but Herman Ese'ese gave away a silly penalty after holding onto an opponent's jersey once the ball had left the area.

It proved to be the Dolphins' last genuine crack at victory.

The Knights' five-game winning streak has seen them rocket from 14th to sixth on the ladder, with their finals destiny now well and truly in their hands.

In contrast, the Dolphins (8-12) have lost seven of their past eight games to crash out of contention.

Fixtures

Ladder