Newcastle coach Rick Stone apologised to fans after the Knights capitulated to a 32-22 loss to Canterbury and presented South Sydney with a golden opportunity to steal their NRL top eight spot.

Captain Kurt Gidley described Newcastle's second half effort as "embarrassing", while Stone said his men simply don't deserve to go to the finals if they play like that.

The Knights cruised to a 22-6 halftime lead and, at that point, losing seemed a near impossibility.

But the Bulldogs made a complete transformation in the second half and secured the win with a stunning double from fullback Ben Barba in the final 10 minutes, which included arguably the best try of the season.

A Newcastle win would have heaped all the pressure on the Rabbitohs to upset an in-form Brisbane at Suncorp Stadium on Sunday in order to keep their finals hopes alive.

But now Newcastle and South Sydney will quite simply play-off for the final position in the NRL top eight in an epic clash on Friday night at Ausgrid Stadium.

It will be winner takes all, but right now the Knights are shell-shocked and sorry after three straight losses.

"I just want to say if you defend like that and you have that sort of intent or lack of, you might as well not be in the finals and that's the way we're looking at it too," said Stone.

"We're embarrassed, we're disappointed ... there was some things that went on today that are not acceptable and I apologise to the fans and the members and everyone involved in our club because it's not good enough."

Gidley led the way in a dominant first half - scoring the opening try and booting two penalty goals to go with tries to Richie Fa'aoso and Zane Tetevano.

The skipper was at a loss to explain how the Knights let their stranglehold slip.

"I don't know, I don't know what happened, I'm still trying to work it out and process what happened in the second half," he said.

"I'm embarrassed about our second half, we should have been fresh we should have come out firing."

To add to Newcastle's worries, centre Keith Lulia suffered a season-ending knee injury, while Tetevano did his hamstring, to add to a casualty ward that already includes Adam MacDougall and Matt Hilder.

Canterbury coach Jim Dymock said it was all about holding onto the ball - his side completed just five sets in the first half before surging back.

Barba showed lightning footwork with 10 minutes left to get the Bulldogs in front.

Then in the 75th minute, he chased a Jonathan Wright kick to execute one of the great put-downs of all time.

The ball bounced on and was destined to go dead before Barba, with his feet millimetres inside the chalk, showed no regard for self-preservation, plummeting head-first for the ground and somehow forcing the ball inside the line.

"The second half the boys showed plenty of heart and that's what I asked them to give and they gave it to me," said Dymock, whose side would need more than a miracle to still make the finals.

"Only special players can do special things like that and Benny Barba, he's a freak."

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