NRL: St George Illawarra Dragons thump Brisbane Broncos to earn semifinal spot

It seems St George Illawarra's late season fadeout is officially over.

The form guide was thrown out the window after a first half hat-trick by Tariq Sims propelled the Dragons to a stunning 48-18 NRL elimination final win over title contenders Brisbane at Suncorp Stadium.

The Dragons booked a semifinal showdown with South Sydney on Saturday with the seven tries-to-three romp in front of 47,296 mostly shocked fans - St George Illawarra's first victory at the venue since 2009.

Remarkably the Dragons claimed their first finals win since their 2010 title after playmaker Gareth Widdop (shoulder), James Graham (concussion) and NSW lock Jack de Belin (ankle) failed to finish the game.

Brisbane are suddenly out of the title race after having their streak of seven straight finals wins at Suncorp sensationally snapped.

Dragons coach Paul McGregor admitted they had been written off before the game.

"But that's pretty normal isn't it?" he laughed.

"But I had confidence right through the week.

"We showed really good character. It's an outstanding victory."

The Dragons weren't expected to show much resistance after leading the ladder up until round 16, only to limp into the finals in seventh with six losses in their past nine games.

The omens weren't good when Brisbane jumped to a 10-2 lead after 17 minutes, but St George Illawarra came alive off a string of Korbin Sims errors to pile on four tries in 18 minutes - including three to his brother and backrower Tariq Sims - to snatch a shock 28-10 halftime lead.

Brisbane threatened to launch a comeback when Widdop came off in the 55th minute after aggravating a shoulder injury that had sidelined him for the last three weeks.

The Broncos scored twice in three minutes to cut the deficit to 34-18, but the Dragons stood up with ex-Broncos halfback Ben Hunt steering his team without Widdop in a happy homecoming after copping vile social media abuse during his side's late season stumble.

"He gets the blame for a lot of things he shouldn't. I am glad he is in the sheds smiling," McGregor said of his maligned No.7 who was booed before kick-off.

Hunt will have to step up again next week after McGregor admitted Widdop was "no chance" of recovering but backed de Belin and Graham to bounce back.

Brisbane also had their share of injuries losing key forwards Joe Ofehengaue (concussion) and David Fifita (ankle).

Instead of another title, Brisbane coach Wayne Bennett is now expected to contemplate his future after the Broncos board knocked back his proposal to stay on to the 2020 season.

He is locked in for 2019 but there is speculation Bennett may not see out his contract.

"Everyone expected us to win and we haven't won one of those games all year - it's maturity," Bennett said.

Bennett hailed Sam Thaiday as "the most popular Bronco" after the loss ended the ex-Test prop's 16 season career.