Both teams managed 138 runs off their regulation 20 overs before taking eight runs apiece from their super overs, the Thunder awarded the win having scored more boundaries.

Channel Ten delayed the start of their 5pm news to take in the closest finish in Big Bash history, with 17,346 fans crammed into the SCG by the time the game finished.

The reigning champion Thunder now sit just a point outside the top four with three games still to play.

A powerfully struck on drive to the boundary by Alyssa Healy off the first ball of the Sixers' super over, bowled by Rene Farrell, swung the momentum to the home side before the wicketkeeper was run out next ball with her side still needing five runs to win.

Captain Ellyse Perry then hit a two through cover before picking out Erin Osborne at long on with three runs still required.

Another run out followed before Ashleigh Gardner could only manage a single off the last ball when two runs were needed.

Stafanie Taylor was the Thunder's star before the super-over madness, belting 68 from 51 balls with seven fours and a six.

Poor fielding cost the Sixers as they narrowly failed to defend 7-138, with three chances going begging in the space of 17 balls at one stage during the run chase.

Gardner, who helped herself to a stylish half century for the Sixers during the regulation overs, said her team had let the win slip through their fingers.

"It goes back to catches win matches for us, I think we did drop Stafanie Taylor quite early and that affected us in the end," Gardner said.

"We had an awesome start to the super over by hitting a four and I think we just let it go a bit.

"We probably should've got across the line but I guess that's what happens in cricket.

"I don't think it's a bad thing to lose this far in the season.

West Indian Taylor was dropped by Emily Leys on 23 off the bowling of Kim Garth before Harmanpreet Kaur edged one to the boundary past wicketkeeper Alyssa Healy. Garth then dropped a difficult chance from Taylor off her own bowling, capping a frustrating afternoon for the Irish import.

Had the Sixers prevailed they would have equalled the eight consecutive wins managed by the Melbourne Stars men's team in BBL 03.

Meanwhile the Thunder could be without Indian superstar Kaur should they progress to the WBBL finals, which would clash with a national training camp as the Indian women's team prepare for an ICC World Cup qualifier.

The Board of Control for Cricket in India have the power to withdraw Kaur from the Big Bash if she is required for national duty.

"It totally depends on the BCCI, whatever they're going to call, I'm going to stick with that," Kaur said.

"They only gave me permission to play here so if they call me I have to go back."