Dejected Broncos players.

The 2019 season appears set to be Wayne Bennett's last as coach at the Brisbane Broncos now that the seventh club premiership he needed to secure a contract extension has slipped away.

The 48-18 thumping St George Illawarra handed out in the elimination semi-final at Suncorp Stadium exposed Brisbane's defensive frailties and the lack of experience in finals football of too many of the club's forwards.

Bennett conceded as much after the loss while deflecting questions about his long-term future at the club, which hung on an unlikely surge to the premiership.

Post-match the Broncos players stayed on the field for more than an hour and drank beers with Sam Thaiday to farewell the club legend.

Bennett joined them for a while after admitting at the post-match presser to his side's weaknesses.

Brisbane conceded 500 points in the regular season, the worst of the eight teams who made it to the finals.

With Alex Glenn, Jaydn Su'A and Matt Gillett all out injured their lack of specialist edge defenders was exposed as the Dragons made hay.

Apart from rampaging 18-year-old back-rower David Fifita the performances of finals debutants Korbin Sims, Matt Lodge and Tevita Pangai jnr, in the game that counted most, was below the bar they had set in the regular season.

Brisbane's habit of giving opponents far too many metres down the middle of the field proved costly, as they failed once again when installed as pre-game favourites.

"We have had three constants all year - the injury toll, expectation, every game we were expected to win we have played badly in... the third one has been our defence, it hasn't been where I want it to be," Bennett said.

"Those three things got exposed. We've lost two of the best edge forwards in the game and our best performances have been against the best teams.

"Teams we thought we could beat, we lost our way. All week it's been about us and how good we were going, which we were.

"That was my biggest fear, the expectation would raise its head again and choke us. Finals are about managing expectation and we had too many young guys in our team."

As for whether he thought he would or should get a contract extension when the Broncos board meets in October, Bennett said "that is not today's conversation".

" I am not going to discuss it," he said. "The season has been tough on everyone, no tougher on me than anyone else. To our credit the boys responded well, it was just disappointing we couldn't nail it here today."

Retiring Broncos legend Sam Thaiday.
Retiring Broncos legend Sam Thaiday. ©Scott Davis/NRL Photos

Korbin Sims, whose next game will be for the Dragons in 2019, said four days ago that the Broncos would look to use brother Tariq's "over aggression" against him in the elimination final showdown.

The reverse happened but Korbin didn't need any assistance from the Dragons on an afternoon he will want to forget in a hurry.

You could analyse the penalties that Sims gave away, which gave the Dragons field position and subsequent points, or the tackle he missed when Tariq powered through him to score.

In the end it was Brisbane's defensive frailties and lack of big game experience in the forwards which counted against them more than any of Sims' failings.

It was sad finish to the season for Brisbane and a sad one for Thaiday, who will be remembered for all the right reasons.

"Sam is the most popular Bronco," Bennett said.

"We will all miss him, he's been great for the club. I will miss him for all the work he does behind the scenes with the young players. He's been calming for them."