Glory missed out on the chance to secure a top-four finish as a brace from Besart Berisha consigned them to a 2-0 defeat at the hands of finals hopefuls Western United.
The former Brisbane Roar striker bundled home his first goal just short of the half-hour mark before doubling his and United's tally from the penalty spot early in the second period following Ivan Franjic's foul on Connor Pain.
Glory's best chances fell the way of Bruno Fornaroli and Neil Kilkenny, with the former flashing an overhead kick wide of the target in the first half and the latter forcing United 'keeper Filip Kurto into an alert stop early in the second.
The result means that Tony Popovic's side will finish either fifth or sixth depending on how United fare in their remaining two games of the regular season against Sydney FC and Melbourne City.
And the Head Coach insisted that there were positives from the United game that his charges will take into their Finals campaign.
"It was a vast improvement from the other day, that's for sure," he said.
"We put the Victory game aside, we played a team that is experienced and in good form and really weren't troubled.
"We conceded two goals from set-pieces and they won the game, so congratulations to them, but if we're going to judge the performance... it was much-improved and we got some minutes into players who have not had a lot of minutes throughout the year.
"I thought the performance was good.
"We didn't give a chance away in the entire game and I don't think Liam [Reddy] had to make a save, so it was a vast improvement in terms of our defensive display.
"We looked dangerous around the box, but it didn't really fall for us.
"We had some players that were missing today, a few with injuries and niggles that weren't available, but I think this performance will put us in good stead for ten days' time.
"We'll be ready for whoever we play."
In a first-half of relatively few chances, Glory came close to taking the lead when Kilkenny's free-kick was met by Fornaroli whose spectacular volley flew wide of the far post.
But seven minutes later it was Mark Rudan's men who broke the deadlock, Cameron Burgess' left-foot cross into the area being parried by Liam Reddy into the midriff of the onrushing Berisha and the ball then rebounding into the back of the net.
1-0 became 2-0 on 51 minutes, Franjic's challenge on Pain deemed worthy of a penalty by referee Chris Beath and Berisha duly sending Reddy the wrong way from the spot to claim his 18th goal of the season.
Glory's response came in the form of an angled strike from the overlapping Dane Ingham which flew over the bar and Kilkenný's curling effort on the hour-mark which drew a one-handed save from Kurto.
The Polish 'keeper was called into action again in the 77th minute, this time getting down well to claim a free-kick which Fornaroli had bent around the wall and that was as close as Glory came to claiming a consolation in the latter stages.
Perth Glory 0 Western United 2 (Berisha 27', 52' (pen))
Bankwest Stadium, Parramatta
Referee: Chris Beath
Assistant Referee 1: Ryan Gallagher
Assistant Referee 2: James Cleal
Fourth Official: Tim Danaskos
Perth Glory: 33.Liam REDDY (GK), 3.Jacob TRATT, 5.Ivan FRANJIC (20.Jake BRIMMER 65'), 9.Bruno FORNAROLI, 16.Tomislav MRCELA, 21.Tarek ELRICH, 23.Dane INGHAM, 27.JUANDE (22.Vince LIA 82'), 28.Gabriel POPOVIC (7.Joel CHIANESE 65'), 29.Kristian POPOVIC (25.Carlo ARMIENTO 82'), 88.Neil KILKENNY (C) (8.James MEREDITH 65')
Substitutes not used: 50.Daniel MARGUSH (GK), 61.Yianni PERKATIS
Yellow Cards: G.Popovic
Red Cards: None
Western United: 1.Filip KURTO (GK), 2.Aaron CALVER, 4.Andrew DURANTE, 6.Tomoki IMAI, 10.Steven LUSTICA, 11.Connor PAIN, 14.Max BURGESS, 18.Besart BERISHA (9.Apostolos STAMATELOPOULOS 86'), 19.Josh RISDON (5.Dylan PIERIAS 61'), 22.Tomislav USKOK (21.Sebastian PASQUALI 90+2'), 23.Alessandro DIAMANTI (c) (26.Patrick ANTELMI 90+2')
Substitutes not used: 15.Jonathan ASPROPOTAMITIS, 17.Joshua CAVALLO, 30.Ryan SCOTT (GK)
Yellow Cards: Pain, Uskok
Red Cards: None