Thursday night's win caps a remarkable turnaround from the Heat, who sat last on the BBL ladder in the second week of January before winning seven of eight games.

Brisbane will meet the Perth Scorchers at Optus Stadium on Saturday in their second grand final appearance.

Without their India-bound talisman Steve Smith, the Sixers sputtered to 9-116 on a tricky SCG wicket.

But missing their own Test stars Usman Khawaja, Marnus Labuschagne and Matt Renshaw, a Heat win was far from assured and they threatened to bottle the chase by losing 3-10 and then falling to 5-56.

With the game on an even keel late, Neser (48 not out) hit Hayden Kerr for four consecutive boundaries in an over that defined the game and sealed one of the great BBL upsets with 10 balls to spare.

"I was just fortunate that that came off," Neser told reporters.

"I normally am quite nervous but it was potentially the last game of the season, so I just thought, it's all or nothing really."

Batters have struggled at the SCG all summer long and when the hosts elected to bat, Brisbane's Matthew Kuhnemann (3-17) and Spencer Johnson (3-28) posted the best figures of their BBL careers.

After catching Kurtis Patterson (19) to break a promising opening partnership, spinner Kuhnemann claimed out-of-sorts opener Josh Philippe (16) and skipper Moises Henriques (four) in the space of two overs.

The quick dismissals forced the Sixers back into their shell and they never got going again, managing 2-8 in the power surge and failing to hit a six all night.

Johnson denied Dan Christian (seven) a fairytale in his last game at the SCG with a length ball that careered into the wicket, before he had the Sixers' last recognised batter Hayden Kerr (16) out caught and bowled.

Daniel Hughes, the Sixers' odd man out for most of the summer, top-scored with 23.

"We just seemed to take wickets at the right time and their batters didn't seem to get a roll on," Neser said.

The Heat found the boundary more easily than the Sixers early on, announcing their intention when Josh Brown hit Steve O'Keefe for six on consecutive deliveries.

One of three replacements for the Heat's Test players, Sam Heazlett tried to sneak a single on a misfield but found himself run out to trigger a collapse. In the space of 21 balls, the Heat also lost Brown (20) and Nathan McSweeney (five), both caught behind by Philippe.

Losing more scalps was the only thing that could thwart the Heat when a run a ball was all that was required and Max Bryant, another of the reinforcements, forged a game-high 30-run partnership with Neser.

Just as they were beginning to pull ahead with the largest partnership of the night, Bryant (11) sent the ball skyward in the power surge and was caught.

But Neser was undeterred and his 16 runs from four balls brought the equation squarely into the Heat's favour.

When he slogged the ball past long on, he had the biggest score of his BBL career.

"(Neser) played a pretty smart innings, which you have to give him credit for," Henriques said.

The Sixers' play-offs campaign came to an end in straight sets after they lost their qualifying final against the Scorchers last week.

"We had two cracks at making the final and unfortunately weren't good enough to take either of them," Henriques said.

"I'm still very, very proud of what we were able to achieve as a team throughout the season."

Australian Associated Press