Townsville star Suzy Batkovic couldn't lift the Fire to win in her 300th WNBL game, despite shooting a game-high 23 points against Canberra.
The four-time league MVP, who became the 17th WNBL player to reach 300 games, led the match for rebounds (12) and assists (5) in the 73-67 loss on Saturday.
Her former Opals' teammate Marianna Tolo was the star for the Capitals, shooting six-of-11 from the field and sinking four of her five free throws for 17 points as she took control of the match.
The defending champions Fire were dealt a big blow three minutes into the first quarter, when they lost American guard Natasha Cloud to a toe injury.
They never recovered, failing to reclaim the lead from midway through the opening term despite going to the first break at 17-17.
The result snapped a five-game winning streak for the defending champions, and allowed sixth-placed Canberra to move within one win of them, and two from the top four with seven games to play.
It was also a cruel blow for the Fire, who missed the chance to sneak into the top four after Bendigo were beaten 71-68 by second-placed Sydney on Friday.
The Spirit didn't hold the lead at any point, but could have sent the match to overtime had a Kelsey Griffin three-point attempt bounced in off the rim on the buzzer.
Sydney joined ladder-leaders Dandenong on 12 wins, albeit with an extra game played.
"We were pushed both games," Sydney coach Cheryl Chambers said.
"They were really close games. But I thought at the end we kept our cool and were able to come away with the wins."
In the weekend's other game, Dandenong overcame Melbourne in the final quarter to win 73-61, with American Ally Malott scoring 24 points.
