A 90th-minute strike from Steven Lustica secured a sixth win in seven games for United and made its place in the Finals safe. 

Besart Berisha put the visitors ahead at Leichhardt Oval, reacting quickest to prod home after Alessandro Diamanti's effort had been parried upwards by Andrew Redmayne. 

Diamanti rattled the crossbar with a magnificent effort from near the halfway line but Sydney was level 52 minutes in when Adam Le Fondre headed in his 20th goal of the season. 

However, Lustica swept home from Dylan Pieras's cross to claim victory, as Sydney's trophy celebrations were somewhat soured after a fifth game in a row without a win.