The Mariners' vital three points, secured at Porirua Park thanks to goals from Annalise Rasmussen and Isabel Gomez, came after a five-game stretch in which they managed two draws and three losses.
Central Coast (28 points) are now fifth on the table after shooting clear of Brisbane Roar (25), who are away to Adelaide United on Sunday.
Canberra United (24) and Wellington (23) stumbled in the scramble for top-six spots on Saturday, with the former suffering a 1-0 loss to Sydney FC at home.
There are a further three rounds to play after this weekend.
"I don't know if it's completely over but it obviously means we've got to win the next three games in a row to stand any chance," Phoenix coach Paul Temple said of his side's finals hopes.
"We're down to must-wins and cup finals now.
"We'll keep going until it's mathematically impossible. We'll keep going until we can't go anymore."
Central Coast goalkeeper Sarah Langman marked her 100th A-League match in style, denying a sizzling long-distance shot from Manaia Elliott late in injury time to earn a clean sheet.
A header from Mariners young gun Peta Trimis went close to breaking the scoreless deadlock in the 44th minute, but the Phoenix's desperation to clear the ensuing danger resulted in a penalty for Rasmussen.
Rasmussen converted to claim a 1-0 halftime buffer, with Gomez doubling the visitors' lead with her powerful strike in the 52nd minute.
Meanwhile, Sydney FC midfielder Mackenzie Hawkesby's 78th-minute goal in Canberra ensured her side extended their purple patch.
The Sky Blues have now won three of their past four games.
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