Melbourne City's 2-0 win over Wellington meant Macarthur simply couldn't afford to lose to the struggling Glory in Perth.
But it all went pear shaped for the Bulls, with goals to Nicholas Pennington, Gabriel Popovic and Arion Sulemani lifting Glory to just their seventh win of the season.
The result left Macarthur four points adrift of sixth spot with just two games remaining.
And given their vastly inferior goal difference, Macarthur will need to win their final two games - against Adelaide and Wellington - and rely on City not picking up more than a single point.
Defending champions Melbourne City round out their campaign with games against Brisbane and Adelaide.
Macarthur could also sneak in if they win their last two games and fifth-placed Melbourne Victory lose to Newcastle Jets and Western Sydney.
"We have to hope for a miracle where we win our last two and City lose both their games," Sterjovski said.
"So it's still possible for it to happen. When there's still a chance to make the six, they don't need motivation.
"It's just the desire to be in the six - everyone wants to play finals football. So as long as it's mathematically there, we should be motivated for every match."
If Macarthur do somehow make the finals, Sterjovski is confident they could cause some damage, especially after beating top-two sides Newcastle and Auckland in the lead-up to Sunday's loss.
"Definitely," Sterjovski said.
"Once you make the finals, anything can happen. And we definitely have the players who could make a difference on their day.
"On our day, we've proven that we can play well against the top teams.
"We've beaten the top two in the last few weeks. It's just consistency has kind of killed us this season."
Glory are almost certain to avoid the wooden spoon for the first time in three years.
Their big question now is whether they will re-sign first-year coach Adam Griffiths, who has helped spark more life into the team following the early-season axing of David Zdrilic.
A season-ending foot injury to star recruit Tom Lawrence was a major reason behind the club's recent eight-match winless run, but Perth achieved victory against Macarthur despite also being without skipper Adam Taggart (adductor).
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