Adding insult to injury, on top of conceding an extra-time winner to Central Coast, Perth Glory are now facing the rest of the season without veteran defender Scott Jamieson.
Jamieson landed awkwardly after an aerial challenge midway through the second half and had to be carried from the nib Stadium pitch on a stretcher.
Glory coach Alistair Edwards confirmed post-match that the 25-year-old would have surgery first thing on Sunday morning and all but conceded the Socceroos hopeful was unlikely to play again this season.
"I'm not sure how long it takes for an Achilles rupture, but he will be out for a considerable amount of time," Edwards said.
"I'm one of many who believe that he was pushing for a Socceroos position. He's been very consistent, playing some great football.
"He's been absolutely quality, but he's distraught."
Jamieson's departure came just minutes after Edwards had made his third and final substitution of the night, leaving Glory to play out the match with just 10 men.
Perth had earlier lost marquee signing William Gallas to a calf injury in the first half, but Edwards did not expect the former French international to miss more than one game.
Gallas, 36, made his first start for Glory and almost scored one of the goals of the season before hobbling from the pitch.
"William trained extremely well during the week and I think he was probably erring on the side of caution," Edwards said.
"He felt something and wanted to come off. We got a good 30 minutes for him, but I think with him being the professional that he is, he wanted to make sure he didn't do anything that would be too long standing."
Glory took the lead against the Mariners through young striker Jamie Maclaren after 24 minutes, but that was cancelled out by Michael McGlinchey's long-range goal only 10 minutes later.
But Jamieson's absence was exposed in the final minute of injury time as an unmarked Mitchell Duke volleyed a cross from Josh Rose into the back of the net for the winner.
"To lose in the last second like that is a bit hard to take, but that's football," Edwards said.
"It throws some challenges at us, but we'll be right because there's a lot of positives in the way that we're playing.
"There was a 10-minute spell in the first half where they (Central Coast) got on top, but apart from that it's probably the best we've played."
Brandon O'Neill and Jack Clisby are the leading candidates to replace Jamieson at left back as fellow youngster Josh Risdon is still months away from resuming from a serious knee injury.
New Central Coast coach Phil Moss, meanwhile, jokingly admitted he would have pointed the finger at Graham Arnold if his side had lost to the Glory.
Arnold handed the reins of the Gosford-based club over to his long-time assistant Moss last week after he accepted an offer to coach J-League side Vegalta Sendai.
But Arnold had already put plans in place to help the Mariners end a three-game winless streak in Perth, including a bold decision to fly west on the day of the match.
The Mariners stayed overnight in Sydney before flying to Perth early Saturday morning in a move that paid dividends for the reigning A-League champions.
"I told Arnie if we lost I was going to blame him and if we won I was going to say it was my first big decision," a smiling Moss said post-match.
"We decided to do it a couple of weeks ago, so the bookings were all made and it was too late for me to change it.
"It's something the staff have been discussing for a couple of seasons now…it was a calculated risk, but it's paid off."
The last-gasp win lifts Central Coast back into top-six contention after claiming just five points from the first five rounds of the season.
Moss admitted "celebrating like a fan" when Duke's injury-time volley found the back of the net, but stressed the victory was not about him or Arnold.
"I said to the boys before the game this wasn't about Graham Arnold leaving the club or me taking over – it was about them," Moss said.
"The game of football is about players and supporters and I was just delighted for them because they handled what's gone on in the last 10 days with so much dignity and such a great attitude.
"For them to come out the end of that with three points and to win a game like that is such a good way to win a game. My players fully deserve it."