In a potential BBL farewell for Brisbane cult figure Chris Lynn, the Sixers easily defended their 6-178 at the Gabba on Wednesday with the Heat slumping to 4-43 in the ninth over and finishing 27 short at 8-151.
It means, unless the Sydney Thunder can notch a monster victory against the Melbourne Renegades, the Sixers will play table-topping Perth Scorchers on Saturday at Marvel Stadium for a spot in the final on January 28.
Lynn passed 3000 BBL runs on his way to making 19 before slapping uppishly to cover, a familiar scene in a season in which he's passed 32 just once in 12 innings.
The slump is a far cry from the form he was in, despite a host of injury setbacks, when he signed a rich, five-year deal that expires this season.
The loyal Heat servant, replaced as captain by Jimmy Peirson this season, could be forced to look elsewhere or retire from the BBL and continue to tour the international T20 circuit.
Brisbane's loss leaves the Heat in danger of collecting the wooden spoon, the Renegades able to overtake them with a win over the Sydney Thunder later on Wednesday.
The Thunder could still jump the Sixers on run-rate, but Daniel Hughes (59 off 45) and Moises Henriques (28 off 18) did their best to put them out of reach on a warm afternoon.
Marnus Labuschagne's dismissal of Henriques in his return from Test duties and Michael Neser's 3-39 ensured the hosts kept things respectable.
Lynn's exit after a bright start was followed by Labuschagne's for just three, while the returning Nathan Lyon found Sam Heazlett's edge to make it 4-43.
Peirson (42 off 23) and Max Bryant (56 off 55) combined to put some pressure back on the Sixers, Bryant notching back-to-back BBL half-centuries for the first time.
The jig was up though when the captain holed out to the miserly Stephen O'Keefe (1-21 off four), leaving them 51 to get off 19 balls before Bryant followed soon after.
Hayden Kerr (3-23) took his tournament tally to 22 wickets, one shy of leading wicket-taker Peter Siddle.
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