Striker David Williams returned to haunt former A-League club Melbourne City, scoring the only goal in a pulsating 1-0 win for the Phoenix in Wellington.
Williams' first-time shot in the fifth minute decided a willing contest on Saturday between two top-six clubs, with the home side dominating the first half but barely clinging on in the second.
Wellington's seventh win of the season further cements their path towards the playoffs, lifting them one point behind City, who are guaranteed to remain fourth by the end of round 16.
Williams, who played more than a century of matches for the City Blues, was arguably the game's best player with his work rate and incisive attacking forays. He bagged a sixth goal in eight games when latching onto a bobbling Liberato Cacace cross, slamming the ball into the top right corner with his left foot, giving Eugene Galekovic no chance.
The visitors protested that Roy Krishna had been offside earlier in the movement but the VAR ruled in favour of the hosts in a tight call. Galekovic was busy for the remainder of the half, making sharp saves from Williams and Tom Doyle.
While the Phoenix had four shots on target to none in the first spell, that statistic reversed after the break as City poured numbers forward with increased confidence.
Goalkeeper Filip Kurto was the Phoenix standout, the Pole expertly denying substitute Moudi Najjar twice, along with a close-range Lachlan Wales strike and a late Riley McGree bullet.
The Phoenix looked more threatening with the inclusion of Williams and Sarpreet Singh, who were benched for Wednesday's 1-0 home loss to Sydney FC.
Warren Joyce also made two changes to the City side who beat Western Sydney 4-3, introducing Wales and Nathaniel Atkinson for Luke Brattan and Curtis Good. Defender Ritchie De Laet again started at striker in the absence of Bruno Fornaroli.