Chasing Canterbury's demanding total of 143 for four, the Sparks gave the target a nudge but could not find a solid foothold.
Players nibbled away at the target rather than tearing chunks out of it.
Suzie Bates got a start, getting through to 22 before she departed.
Katey Martin compiled a smart 15 but was trapped in front, and Lisa Grant whacked a quickfire 40 from 32 deliveries then offered a catch just when she was looking threatening. Had the players been able to synchronise their efforts and form a meaningful partnership, the end result may have been different.
Instead, the Sparks fell 14 runs short.
Clare Taylor (22 not out) and Victoria Abbott (11 not out) added 27 in a useful and unbeaten stand for the seventh-wicket. But the pair could not keep pace with the run rate. They required 26 off the last two overs but could only manage 12.
Otago needed to win to retain any chance of reaching the final and will now turn its attention to the one-day tournament.
The Sparks need to beat Canterbury in Christchurch today and hope Wellington loses to Central Districts in Palmerston North.
Earlier, Canterbury's Amy Satterthwaite (63 not out) and Maria Fahey (51 off 46) combined in what proved to be a match-winning partnership.
The pair added 85 for the third-wicket after their side was struggling at 14 for two.
