But at least the Wellington side have something to build on, with five of their next seven matches on home soil.
Sitting at the bottom of the table, and with the playing squad feeling partly culpable for Ernie Merrick's departure, there was always going to be a response. It happens across all sports - as players are infused with energy - but it is often short lived.
Interim coaches Chris Greenacre and Des Buckingham tinkered with the formation, with Hamish Watson installed to lead the line, Barbarouses and Roy Krishna playing either side of him and Roly Bonevacia used as a holding midfielder.
There was more energy than we have seen in recent weeks, but the Phoenix struggled to retain possession in the first half, and when they lost it, took a long time to get it back. The Mariners - whose young roster lacks any star quality - looked much more comfortable on the ball, though usually not in dangerous areas.
Waikato Stadium was the seventh venue the Phoenix have used outside Wellington, but they may not be going back in a hurry. The playing surface was perfect but it was a poor turnout from the Waikato football fraternity, though the awful weather conditions earlier in the afternoon didn't help.
The Phoenix made the perfect start. Barbarouses finally opened his account, scoring after just 80 seconds. With defenders retreating, the All Whites forward ran from just beyond the halfway line, before finding the net (via a deflection) from the edge of the area.
The Phoenix, who have lost just two of 17 matches in New Zealand outside Wellington, always looked more likely in the second half, with Watson hitting the post and crosses zipping across the six yard box.
There was finally a dividend, when Lia - who had found the net just three times in more than 200 games before last night - hit a screamer. Using perfect technique, he produced a perfect shot from 30 yards into the top corner. It was a collectors item, that sealed a much needed three points, before Krishna's late strike.
Wellington Phoenix 3 (K Barbarouses, V Lia, R Krishna)
Central Coast Mariners 0
Halftime: 1-0