A fine strike from Isaias ended Adelaide's goal and win drought, with United grinding out a 1-0 win over Central Coast in Gosford.
Adelaide hadn't managed to score for just over 350 minutes before their skipper pounced on a headed clearance and rifled a volley home from the edge of the area in the 35th minute of Sunday's clash.
Securing their first win in six A-League games, Adelaide leapfrog Melbourne City into fifth, eight points ahead of seventh-placed Newcastle with four rounds remaining. The Mariners remain last.
Central Coast had the better opportunities in the first half but struggled to create much after the break against a well-drilled United side.
The Mariners played with 10 men from the 72nd minute, when captain Jem Karacan picked up a second yellow card.
He was booked in the first half for kicking the ball away and referee Kurt Ams showed him a second yellow for a foul on Michael Jakobsen.
Central Coast striker Jordan Murray headed straight at Adelaide goalkeeper Paul Izzo early on and had another on-target effort later in the half, while Karacan and Aiden O'Neill wasted chances.
The Mariners created little in the second half, with Adelaide controlling much of the play and looking more likely to score, though Mariners Connor Pain and Matthew Millar were off target with stoppage-time shots.