An early strike by Connor Pain secured Western United a precious 1-0 A-League win over Central Coast on Saturday.
In the first A-League match to be played in Tasmania in eight years, Pain's fifth-minute goal was the difference at UTAS Stadium in Launceston in a match marked by a confusing VAR intervention in the second half.
Mariners defender Ruon Tongyik's evening looked over in the 61st minute when he was shown a second yellow card for a challenge on Pain.
Before Tongyik could leave the field however he was recalled and his dismissal rescinded after the VAR ruled United striker Besart Berisha was offside in the seconds before the foul happened.
The Mariners however were unable to make the most of their stroke of fortune, as they slipped to their fifth defeat of the season.
The loss means Alen Stajcic's men are in danger of losing the top spot they have held for much of the season, with Adelaide United and Melbourne City close enough to overtake the Mariners by the end of the weekend.
Pain made the most of some static Mariners defending early in the game, working a one-two with Berisha before poking the ball home.
Central Coast were largely outplayed in the opening half but did have their opportunities to equalise with Marcos Urena guilty of a tame finish that was comfortably saved by United goalkeeper Ryan Scott with Daniel Bouman unmarked.
Bouman then created a great chance but Polish winger Michal Janota was denied by a quick-thinking Scott.
United had their opportunities too, with Spanish midfielder Iker Guarrotxena failing to finish after a delightful pass from Alessandro Diamanti had left him one-on-one with Mariners goalkeeper Mark Birighitti.
Young gun Alou Kuol, whose move to German club VfB Stuttgart on a four-year deal at season's end was confirmed on Friday, came on in the second half and gave United's defence plenty to think about but the Victorians held on for a win which keeps them in touch with the top six.
United stay in Tasmania to face Wellington Phoenix on Thursday while the Mariners return home to host Sydney FC at Gosford next weekend.