Otago's semifinal aspirations are over after a forgettable 20-minute spell in Pukekohe on Saturday afternoon.
Trailing 31-24 after Spirit lock Epe Elisara dotted down next to the posts on 60 minutes, the Spirit was right in the must-win match.
However, Counties-Manukau killed off Otago's season with four well-taken tries down the stretch.
Black Ferns winger Renee Wickliffe scored three tries for the home side, including a spectacular 60m effort straight from the kickoff to make it 48-24 inside the last seven minutes.
The loss - Otago's third from five games this season - means it will go into this weekend's final match against Auckland in Dunedin in fifth place on the ladder.
A consolation four-try bonus point on Saturday lifted the Spirit a point clear of Canterbury on 11 points, but there is no way of catching fourth-placed Counties, which has 17 competition points.
Spirit coach Duncan McEwan said the first 60 minutes of the match was the best his team had played this season.
''They executed really well. And then essentially we got to the point where injury and exhaustion forced me to put our bench on ... the girls just buried themselves and we couldn't hold on.
''The score line was not reflective itself of how tough and tight the contest was.''
The Spirit started the match in brilliant fashion when centre Greer Muir bust Counties open at halfway, before gassing a couple of defenders to the line.
Halfback Megan Manson missed the conversion from right in front, but the Spirit led 5-0 after just four minutes.
Counties hit back immediately to lead 7-5 and the tries kept on coming when Spirit winger Hollie Fraser showed good pace to score the third try of the match inside 10 minutes.
Fraser's day ended a couple of minutes later when she picked up what appeared to be a serious knee injury, making a tackle.
The extent of her injury will not be known until she has a scan this week, but McEwan said she had done serious ligament damage and would miss the team's final game.
Larissa Muir, who usually plays in the midfield, replaced her and was left with the daunting prospect of marking Wickliffe.
It was not long before the Counties star scored her first of three tries with some dazzling footwork down the right-hand flank to tie the game at 12-12.
No10 Arihiana Marino made it 17-12 two minutes later when she ripped the ball from Spirit prop Eilis Doyle's grasp and scampered 60m for a try.
There was still more to come for the home side, as it secured a bonus point on halftime through a well-executed rolling maul.
Muir kept Otago within touch with her second try within the first minute of the second half, but Otago faltered through a combination of botched lineouts, fatigue and handling errors inside its own half.
With plenty of backs in the injury ward, McEwan said he would call one or two uncapped players into the squad to play Auckland on Saturday.
Women's rugby
The scores
Counties-Manukau 55
Renee Wickliffe 3, Shontelle Dudley, Arihiana Marino, Sharnita Woodman, Aroha Savage, Hinewai Pomare, Cynthia Ta'ala tries; Marino 5 con
Otago Spirit 24
Greer Muir 2, Hollie Fraser, Epe Elisara tries; Megan Manson 2 con
Halftime: 24-12 Counties
