The team slumped to a 37-run loss against Auckland at Molyneux Park yesterday.
Hearts opener Anna Peterson survived several opportunities and went on to club 68 from 51 to help her side post 156 for three.
The total was Auckland's eighth highest and its highest against the Sparks.
And critically, it was too many for its opponent.
Otago managed 119 in reply thanks largely to Polly Inglis, who flayed her maiden T20 half-century in a desperate attempt to rescue her side from an early collapse.
She played nicely for her 62 but had virtually no support.
The Sparks host Canterbury at the venue today and coach Craig Cumming said his side needed to grab its opportunities.
"We created them, so that was positive," he said.
"Had we taken those opportunities it could have been a lot different.
"We would have forced them to play under pressure, but we couldn't and they got in and started playing with freedom and taking our spinners on.
"When you look at the game, that was probably the most important part."
The Hearts set the tone early. Peterson dispatched three fours off the opening over to kickstart the innings.
Emma Black was guilty of over-tossing and got driven down the ground.
Molly Loe hit a better length from the other end. Her opening three overs went for 14 which helped create some pressure.
Gemma Adams got the reward, though. Lauren Down went after a pull shot but mistimed it and was caught at mid-on by Polly Inglis.
Loe should have picked up the wicket of Peterson for 31, but Bhagya Herath dropped a towering catch she never really looked comfortable under.
Peterson climbed into the next over from Eden Carson, sweeping four and dispatching a six down the ground.
She brought up her 50 off 41 balls and was starting to use her feet well to disrupt the length of spin duo Carson and Herath.
The Sparks put down another opportunity to claim her wicket. This time it was flat hit out towards midwicket.
Katie Perkins played a supporting role down the other end and the partnership quickly mounted.
But the Sparks got the breakthrough when Peterson advanced, missed and was stumped by some slick work from Katey Martin off the bowling of Black.
Perkins went in the next over for 25. That helped the Sparks claw back the run rate.
Adams bowled a tight final over in her spell to put a bit more pressure on the brake pedal.
But the Hearts clubbed 17 off the penultimate over to go past 150.
The Sparks chase got off to a catastrophic start.
Millie Cowan (5) and the vastly experienced Katey Martin (0) were bowled before they could get established.
Holly Huddleston got the key wicket of Martin, who was the No1 threat in the line-up.
There was no luck for Jensen, either. She got a leading edge on 12.
The Sparks had collapsed to 38 for three inside six overs.
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