An aggressive Brisbane posted an emphatic 24-10 win over St George Illawarra in an enthralling NRL semi-final at Suncorp Stadium on Saturday night.

But the four-tries-to-two victory came at a heavy cost, with Broncos halfback Peter Wallace suffering a possible season-ending ankle injury late in the match.

Coach Ivan Henjak said it was too early to tell but he was hopeful Wallace could play in Saturday's preliminary final against arch rivals Melbourne at Etihad Stadium.

"We'll wait to see what the damage is with Wal," Henjak said.

"We'll enjoy tonight, they deserve that."

Wallace was rushed to hospital for scans after he suffered suspected ligament damage to his left ankle in the 74th minute.

The Dragons became the first minor premiers since 1993 to bow out of the finals in "straight sets", heaping more misery upon their long-suffering fans.

Wayne Bennett's much-vaunted outfit lost five out of their last six matches to limp out of the premiership race.

But Bennett rejected any suggestion the Dragons had lived up to their reputation as chokers.

"It's just that we were playing our worst football at the wrong end of the season," he said.

"The only thing I promised when I came here was consistency and I think we achieved that."

St George Illawarra will be ruing a litany of errors, mainly caused by some crunching defence from the home side, who have now won seven straight matches for the first time since 2005.

Man-of-the-match Ashton Sims and prop Nick Kenny, in particular, were brutal in defence and deserved the rich praise from Henjak.

The Broncos are surging at the right time of the year after looking out of the running only two months ago.

"We've shown some character in recent months but none better than that," said proud skipper Darren Lockyer.

Brisbane's AFL-bound fullback Karmichael Hunt scored two tries in the first half while Brett Morris bagged his team's only tries.

The Dragons trailed 12-6 at halftime but Brisbane's hard-hitting aggression went into overdrive after the break.

The Broncos effectively killed off the contest through tries to Jharal Yow Yeh and Alex Glenn, both off Wallace kicks.

The lead had blown out to 24-6 after 52 minutes and it was painfully obvious there would be no joy for Bennett, who won six premierships during a 21-year tenure at the Broncos.

It was Brisbane's first finals victory at The Cauldron in seven attempts.

"Our semi-final record is not good here. It was nice to get the monkey off our back," Lockyer said.

The Broncos set a fiery tone from the opening tackle when back-rower Sims smashed Justin Poore, much to the delight of many in the 52,255-strong crowd.

The Dragons had won their previous seven matches at the venue but on Saturday night they were outmuscled and outplayed.

The Broncos' defence - after leaking 32 points against Gold Coast last weekend - was nothing short of magnificent.

Dragons pair Jeremy Smith and Wendell Sailor were both held up over the line shortly before Morris crossed for his second try, 15 minutes before his side's season ended.

Bennett summed up the importance of Brisbane's inspirational leader: "If Darren Lockyer can stand on his feet and captain the side, you never write the Broncos off."

Brought to you by AAP © 2024 AAP