McCullum the Heat's BBL driving force

Joe Burns reckons the Brisbane Heat owe it all to their skipper Brendon McCullum as they hunt a spot in Saturday's KFC Big Bash League final.

The Heat take on the Sydney Sixers in tonight's semi-final at the Gabba, with the winner to face either Perth Scorchers or Melbourne Stars in the tournament decider.

McCullum has been instrumental for Brisbane with 277 runs across his seven innings but according to Burns, his impact in his first year as captain goes far beyond the scoreboard.

"The runs Baz makes is just a bonus to what he brings off the field as captain," Burns said.

"I guess the way he's got us to play the game, our Brisbane Heat identity, it's all come from him.

"He needs to take huge credit for the way the team's playing.

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"In big games, I guess you rely on your big players, and there's no bigger player for us than Brendon McCullum."

Brisbane have not played BBL finals since beating the Scorchers in the 2012-13 final.

However, the return of West Indian leg-spinner Samuel Badree - the tournament's top-ranked bowler according to the BBL's official player ratings - is a considerable boost against a Sixers side that has struggled against tweakers.

"He matches up very well against a lot of their batters so a very key player for us," Burns said.

The Sixers clinched third spot on the ladder with a three-wicket win over the Stars last week, while the Heat let first position slip with a heart-stopping one-run defeat to the Melbourne Renegades.

Burns said the Heat will draw some harsh lessons from that match's manic finish.

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"Not just in the final over, but throughout the game we had opportunities to really run away with it," he said.

"Coming into semi-finals cricket, we know if the game's there to win, we have to not mess around and just win it."

A capacity crowd is expected at the Gabba, where the Heat have won just one of their four games this season - one of those losses coming against the Sixers.

"We've beat them up here, that's good for us," Sixers batsman Daniel Hughes said.

"But we just worry about what we're going to do.

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"Brendon McCullum's their captain, he doesn't really know what they're going to do either - he's full of surprises.

"That's Twenty20 cricket, you can't plan too much."

Brisbane Heat: Brendon McCullum (c), Samuel Badree, Joe Burns, Ben Cutting, Alex Doolan, Sam Heazlett, Marnus Labuschagne, Josh Lalor, Jimmy Peirson, Alex Ross, Mark Steketee, Mitch Swepson, Jack Wildermuth

Sydney Sixers: Moises Henriques (c), Sean Abbott, Jackson Bird, Doug Bollinger, Johan Botha, , Ben Dwarshuis, Brad Haddin, Daniel Hughes, Michael Lumb, Nathan Lyon, Nic Maddinson, Colin Munro, Jordan Silk