Despite both sides requiring a win to secure an advantageous position in the playoffs, the opening to the match was cagey and neither side committed too much going forward.
Both sides blew one-on-one chances after half an hour, with first Bernie Ibini being denied by an advancing Mark Paston before Chris Greenacre, after being put clean through by Paul Ifill, succeeding only in prodding a weak attempt at Ryan.
The Phoenix were looking the likelier side to break to deadlock but, against the run of play, Central Coast struck with a dagger blow right on halftime.
In his 100th game for the Phoenix, captain Andre Durante made a rare error to give away possession and then gave Mariners striker John Sutton too much space in the box.
Sutton gratefully accepted the invitation and guided a glancing header past Paston from an Oliver Bozanic cross for his first goal for the club.
It was a bitter blow for the Phoenix as the trudged into the sheds for the break, with the goal all but leaving them in fourth spot on the ladder, given the Mariners have lost only once this season when opening the scoring.
And that position was confirmed shortly after halftime when Ibini doubled his side's advantage and secured the minor premiership for the Mariners. All Whites midfielder Michael McGlinchey was given too much time in the Phoenix half, and he made the Phoenix pay by slipping through a beautiful ball for Ibini to slot a shot just inside Paston's right-hand post.
Phoenix coach Ricki Herbert responded to the goal by withdrawing Greenacre and Dani Sanchez, with one eye surely on Friday night. And the Phoenix certainly began to play as such, with the Mariners the only side which looked like scoring in the last half hour.
A Tim Brown header which went wide was all the Phoenix had to shout about at the attacking end, before Bertos pulled one back with a spectacular but accidental goal. He was looking for a teammate with a whipped free kick from the left, but overhit his ball and sailed one into the top corner of Ryan's goal.
The Phoenix came alive in the last 10 minutes, but failed to force an equaliser, leaving Wellington to look ahead to finals football on Friday night.
Phoenix 1 (Bertos 80)
Central Coast 2 (Sutton 45, Ibini 51)
HT: 0-1