Western United were defeated 1-0 on Sunday night at the hands of an in-form Newcastle Jets.
With a top six spot up for grabs, both sides attempted to get on the front foot early at McDonald Jones Stadium.
Newcastle opened the scoring in the 29th minute when Roy O'Donovan headed past Filip Kurto at the near post.
Besart Berisha thought he had the equaliser moments later, putting the ball in the back of the net before the goal was ruled out for offside.
United searched for an equalier in the second half - Max Burgess going the closest with a pair of long-range strikes.
The defeat sees Mark Rudan's side fall to eighth on the A-League table, with games in hand over fellow top six challengers, Newcastle and Adelaide.
Newcastle Jets 1 (O'Donovan 29')
Western United 0