The Knights spent only two weeks in the top eight before round 27, but Sunday's win in Newcastle locks up an elimination final date with North Queensland in Townsville next Saturday.
"They will start favourites, being in Townsville. No one had us in the eight to start the year, there might have been one or two of you," said Knights coach Adam O'Brien.
"Everyone will keep us as the underdog. We like it that way. We've been using (our underdog status) all year, we're the ugly ducklings."
The Dolphins' loss brings the curtain down on Wayne Bennett's two seasons as the 17th franchise's foundation coach and ends retiring captain Jesse Bromwich's 338-game career.
Dolphins veteran Jesse Bromwich was sent to the sin bin in his final NRL match. (Mark Evans/AAP PHOTOS)
A maiden finals appearance looked officially out of reach for the Dolphins when Bromwich went to the sin bin in the final 15 minutes for sliding over to hit Ponga high on the ground.
"The overwhelming feeling is that I let the team and the club down," Bromwich said.
"Once that goes away, I'll deal with the whole retirement thing. But it sucks to go out that way."
Superstar fullback Kalyn Ponga threw the last pass for both Knights tries in a gritty affair that went scoreless for nearly half an hour.
After struggling to find his rhythm with the ball early on, the Knights captain scooted out of dummy half to put lock Adam Elliott over with a short ball.
He doubled the Knights' 6-0 half-time lead by strolling almost half the width of the park before finding a space for Brodie Jones to streak over.
Ponga could have had two more try assists if the bunker had not intervened to find knock-ons in the lead-up to both would-be four-pointers.
Adam Elliott opened the scoring for Newcastle in the Knights' final-round win over the Dolphins. (Mark Evans/AAP PHOTOS)
A late shot from Felise Kaufusi left Ponga clutching at his right shoulder midway through the second half, but he finished the game after being cleared by a Knights trainer.
Ponga shook his arms above his head in the press conference to prove the injury had only been a stinger and would not require extra medical attention in the week.
His rival fullback Trai Fuller was the Dolphins' best player all afternoon.
The 27-year-old had an early try denied on the left edge after it was ruled Knights forward Jones had been obstructed in backplay.
Dolphins coach Wayne Bennett was incensed by the call, adamant Connelly Lemuelu had not denied Jones the chance to get to Fuller as he wrapped around to the tryline.
"The four defender will run straight into the guy running through because he knows he's going to get a penalty ... it's just crazy," he said.
"I feel sad for the teams going forward in the next four weeks because someone else is going to pay the price for it."
Fuller came within inches of reaching out for a try in the shadows of halftime but was stopped short amid an afternoon of strong goal-line defence from the Knights.
Hamiso Tabuai-Fidow finally opened the Dolphins' account with 10 minutes to play.
Hamiso Tabuai-Fidow scored the Dolphins' only try in their season-ending loss to the Knights. (Mark Evans/AAP PHOTOS)
The result officially ends the Raiders' mathematical hopes of playing finals.
Canberra had been relying on a draw between the Dolphins and Knights to sneak into eighth spot, but will instead finish ninth ahead of the 10th-placed Dolphins.
The Knights, meanwhile, have secured a fourth finals berth from five seasons under O'Brien.
"I'm just rapt to get the result," the coach said.
"I can't get the smile off my face, but I'll need to, we need to regroup. We've got a job to do up in Townsville next week."
