Otago's prospects of making the twenty20 final vanished thanks to a stunning fourth-wicket partnership by experienced Auckland pair Katie Perkins and Victoria Lind.
The duo put on an unbroken stand of 121 to guide their side to a seven-wicket win with an over remaining at Lincoln yesterday.
The game was shaping as a tight encounter.
The Sparks posted a competitive total of 136 for six thanks to a fine half-century by Katey Martin.
But Perkins, who was playing her 100th twenty20 match, took the game away from the Sparks with 75 from 51 deliveries.
She had tremendous support from Lind who hit 40 from 37.
Auckland moved to the top of the competition standings with the win, while Otago dropped to fifth place.
Sparks captain Suzie Bates perhaps went too hard too early in the game. She had clipped 15 runs from 14 balls when she was bowled by Holly Huddleston in just the third over.
Millie Cowan and Martin made up for the early hiccup with a solid partnership of 43.
Cowan struck back-to-back boundaries in the sixth over and helped take the pressure off Martin, who initially struggled to find her rhythm.
Cowan got through to 28 before she was bowled, and Martin found the middle of her bat in the 13th over with three fours.
That boosted the Sparks run rate and Martin reached 50 from 44 balls. She was bowled for 55 from 48 in the last over but helped get the Sparks through to a decent total.
Regina Lili'i was the pick of the Auckland bowlers with two for nine from three overs.
Auckland made a stuttering start in reply. Bates trapped aggressive opener Anna Peterson lbw for 10 and then bowled Maddy Green (one) before she could get established.
Then Cowan, who had a good match, trapped the other opener Lauren Down in front for five.
Auckland had slumped to 16 for three but had two very wily campaigners at the wicket in Perkins and Lind.
Otago will have an opportunity to rebound with back-to-back one-dayers against Auckland in Lincoln today and tomorrow.
In the other women's T20 matches, Central Districts beat Wellington by two wickets and Canterbury downed Northern Districts by seven wickets. Both games were decided in the last over.
In the men's T20 tournament, Northern Districts overhauled Auckland's total of 142 for six with nine wickets and more than four overs spare. BJ Watling posted an undefeated 53 for Northern Districts and Dean Brownlie added 54 from 34 balls.
