Their prospects look bleak following a seven-wicket loss to Northern Districts in Alexandra yesterday.
The Sparks posted 150 for seven but Northern Districts overhauled the target with more than two overs to spare.
With just two round-robin games remaining for the Sparks, they will need to win both matches and hope other results go their way to make the top three and squeak into the playoffs.
Auckland and Wellington occupy the top two spots with 20 points each, while Canterbury is in third place with 18 points but has four games remaining.
Otago, on 14 points, is in fourth place with three wins from eight games. ND's win lifted it to 14 points but it is in the same situation as Otago.
In all likelihood, the top three will not change. A win would have kept the Sparks in touch with the leaders but they have been left to reflect on a disappointing back end to their innings.
Four wickets tumbled in the last two overs and that prevented the home side from posting a more competitive score.
The Sparks made a tremendous start with openers Millie Cowan and and Alice Davidson-Richards blasting 91 for the first wicket.
Cowan was particularly aggressive. She brought up her maiden half-century off just 36 balls and continued to find the rope until she managed to drag an innocuous delivery from spinner Alisha Rout.
She clouted 12 fours during her 47-ball innings of 61. But her departure brought about a change of fortune.
Northern Districts clawed back the run rate with a series of wickets.
The reliable Katey Martin was bowled around her legs for three when she tried to sweep a delivery which pitched outside off and hit middle and leg.
Classy all-rounder Leigh Kasperek tried to hoof another Rout delivery over leg but got an edge through to the keeper and fell for seven.
Davidson-Richards holed out at midwicket in the penultimate over for an impressive 58 from 40 deliveries. She combined innovation and power and also gapped the ball well.
The next five deliveries yielded a further three wickets - all run-outs - which helped halt Otago's progress.
But it was Rout who turned the game with three for 15.
The Sparks were missing frugal left-armer Kate Heffernan at the top of the bowling order and ND was able to get off to a wonderful start.
Opener Katie Gurrey plundered 79 from 51 balls and featured in a match-winning stand of 112 runs with fellow opener Bernadine Bezuidenhout. The duo made it look easy with Bezuidenhout swatting 49 from 36 balls.
Kasperek, with none off 21, and Eden Carson, who took one for 26, were the best of the Otago bowlers on a day when the bat dominated the ball.
Davidson-Richards was easily the worst. Her one over cost the side 17 runs.
On Saturday, Auckland restricted Central Districts to 106 for eight at Pukekura Park in New Plymouth.
Holly Huddleston, with 25, and Regina Lill'i, with 19, anchored the chase with a 49-run partnership to help secure a four-wicket win for the visiting side.
