The result could hardly be described as too great a shock, given Central Coast ran rampant over the Phoenix last Tuesday. But Wellington switched to a back three after that mauling and appeared to have turned the page with consecutive wins.
Instead, with a chance to move into the top four, the Phoenix conceded four more times to extend their competition-worst defensive record to 43 goals against from 22 games, remaining in fifth.
It was their first loss in Wellington since 2019 - largely kept away by Covid restrictions in subsequent years - and left them looking for a much more enjoyable trip to Eden Park next Sunday.
At least the eighth-placed Mariners will be heading back to Australia, with Western Sydney the opposition in Auckland.
Central Coast did especially well today to withstand the hosts' early salvo in front of 18,000 fans, with a Wellington starting XI featuring five players making their Sky Stadium debuts fired up by the occasion.
The Phoenix began with a predictable verve to their attacking play, earning three shooting chances in the first three minutes and playing very much like a team happy to be home.
They monopolised possession in the opening quarter and unleashed seven shots to one, but few provided a problem for goalkeeper Mark Birighitti.
The Mariners custodian did make a decent stop to deny David Ball in the 26th minute and the save led to the opening goal as a quick-fire counterattack was slotted inside Oli Sail's far post by Beni N'Kololo.
That strike saw the Mariners start to find their footing in the game and they particularly impressed with quick passing combinations to play through the Phoenix.
Worryingly for the home fans, the Phoenix had lost all eight games this season in which they had conceded first, and that trend seemed like it could continue as they remained 1-0 down at the break.
A change of shape in the second half saw Tim Payne pushed into midfield and Gael Sandoval freed up, but the alteration also allowed the Mariners more space to threaten a second.
It soon came, following another spurned chance from Ball, who had done well just to take his place in the team, suffering from a toe injury that left him consigned to a moon boot.
The Englishman failed to apply a clean connection on his header from Sandoval's cross and, just like the opener, the Mariners immediately made the hosts pay as Jason Cummings nodded home after Moresche had hit the bar.
The crowd was further deflated three minutes later as Moresche fired in a third, and when Matt Hatch scored in stoppage time, the Phoenix party had been well and truly pooped.
Central Coast Mariners 4 (Beni N'Kololo 26, Jason Cummings 62, Moresche 65, Matt Hatch 90+6)
Wellington Phoenix 0
Halftime: 1-0
