The result actually sees Sydney FC in to fifth place, pushing above Adelaide United, and avoiding the defending Champions, Central Coast, and they will now head to Melbourne for an elimination final against Melbourne Victory.
With time running out it looked like a trip up the F3 would be in order for Sydney FC, but Richard Garcia sealed the win with one of the last kicks of the match to shift their elimination final to Melbourne instead of Gosford.
It was a poor performance from Sydney FC, and one that will not instill fear in any of the teams in the finals, but will likely leave the Mariners unhappy about playing Adelaide United, the only side in the finals they have yet to beat this season.
Sydney needed to lose by two gaols to not make the finals, and that may have contributed to the lack luster effort from the hosts as Perth were really able to push for a win in the second half.
The pitch at Allianz Stadium still looked poor, although certainly a big step up from the muddy paddock that it was just seven days earlier, making it difficult for either side to hold possession for long periods.
Perth had the first chance of the match as they were able to get the ball forward to Chris Harold who shot agonizingly wide.
Alessandro Del Piero looked to make an impact in his last home match for Sydney and, as his is custom, looked dangerous on an early set piece, which went just wide, despite being at such a tight angle.
Milos Dimitrijevic went close mid-way through the half as he was able to find space just outside the box and hit a powerful shot that went wide.
In the 38th minute Sydney FC had their lead as Terry Antonis was able to make space for himself 30 yards out and unleash a thunderbolt of a shot that left Jack Duncan absolutely no chance.
Late in the half Sydney seemed determined and as the half wound down Seb Ryall nearly found a second goal but he saw his effort denied by Duncan.
In stoppage time Perth drew level after some poor Sydney defense on a corner allowed Rostyn Griffiths to head home the equalizer to make it 1-1 at the break.
The second half saw Perth Glory dominate the match but the scoring chances were few and far between, with Sydney having the only real clear chances of the half.
It was Del Piero who had the first chance of the half as he was able to get space, close in on goal and poke home but was denied as Duncan saved.
For all the work from Perth Glory it was Sydney who found the third goal of the match as a through ball was sent for Garcia who ran on to it and tucked home the winner in stoppage time to seal the 2-1 win and fifth place.