Princess Ibini has kept Sydney FC's unlikely A-League Women finals dream alive, icing a 1-0 win in stoppage time that ends Perth Glory's own top-six hopes.

It came as Western United missed a chance to confirm a home elimination final by losing 3-1 to Adelaide United in Melbourne.

The ALW's most successful club, Sydney had been staring down the possibility of missing finals for the first time in the competition's 17-year history, with the score 0-0 after regulation time on Saturday.

Sydney and Perth, who had sat ninth and 10th on the ladder, each needed a win to remain any chance of playing finals, with a draw or loss to prove fatal before the last round of the regular season.

Sydney had enjoyed the better of chances at Allianz Staidum but were unable to work past Glory goalkeeper Miranda Templeman until the first minute of added time.

Indiana dos Santos floated a long cross across the box to super-sub Ibini, who bamboozled defender Grace Johnston and sent a curling strike into the right side of the box.

The result means the Sky Blues' rags-to-riches story will wage on for at least another day.

The back-to-back reigning champions won only two of their first 16 games this season, before winning five of six to make an unlikely charge into finals calculations.

They will still rely on plenty of other results falling their way to qualify.

Most pressingly, if sixth-placed Canberra United win either of their remaining two games, Sydney will be out of contention.

Goal difference means the Sky Blues also likely cannot afford for seventh-placed Brisbane Roar to win either of their games.

Western United could have locked up fourth spot on the ladder by beating third-placed Adelaide later on Saturday but fell victim to a fast start from the visitors.

Lucia Leon and Sarah Morgan found the back of the net inside 15 minutes, leaving Western United to play catch-up, with Leon confirming her brace in the second half.

Adelaide are already locked into third spot, meaning they'll host a home elimination final for a spot in the final four.

Western United will still finish the weekend in fourth and will still clinch a home elimination final if they beat Wellington next week.

But they could finish as low as sixth if they lose to the Phoenix and other results fall against them across this weekend and next.