Central Coast were surprisingly never in the hunt as last-placed Newcastle upset the Mariners 2-0 in the A-League.
Central Coast have squandered the opportunity to lock away their first A-League finals appearance in seven years, upset by lowly Newcastle 2-0 in the F3 derby at Gosford.
Needing just a point to confirm a spot in the six with a game remaining, the Mariners fluffed their lines on the big stage as the Jets ran out deserved winners.
First-half goals to former Mariner Roy O'Donovan and Lucas Mauragis did the damage, the home side then struggling to play catch-up on a night where the final delivery consistently went astray.
The first quarter was evenly balanced at Central Coast Stadium but O'Donovan's 27th-minute finish set the tone for much of the rest of the match.
It started innocuously enough when midfielder Jordan O'Doherty pumped the ball forward in hope, with Kye Rowles' sloppy headed clearance helping to create something from nothing.
Sixteen-year-old starting debutant Archie Goodwin controlled the proceeds beautifully, releasing O'Donovan who beat 'keeper Mark Birighitti cleanly on the diagonal to make it 1-0.
The Mariners' task became that much harder just six minutes later.
Mauragis's perseverance paid off when he poached the ball from veteran Matt Simon, starting up a movement with best on field Angus Thurgate who cut back to his teammate with the pass of the evening.
Mauragis finished off after a deflection from Birighitti, leaving the Mariners lost at sea, down 2-0.
Well-versed this season in coming from behind, it rarely looked on the cards for the Mariners on Tuesday, Daniel Bouman's 38th minute drive into the back of the net quickly pulled back for Simon's offside.
It was a night to forget for Central Coast stalwart Simon, who was replaced at half-time by Alou Kuol.
While the home side had plenty of possession in the second half they rarely troubled the Jets, who were marshalled superbly in defence.
Still in third (39 points), the Mariners would be fiendishly unlucky not to make the finals with just one game remaining against 10th-placed Western United on Saturday.
Coach Alen Stajcic played down the insipid display on the cusp of the post-season, looking instead at what has been a breakthrough six months for a club that finished last in four of the last five seasons.
"I think we've picked the club back off the ground and we couldn't be any prouder with how our team has performed and carried itself throughout the year," he said.
"And that's not going to change after one sub-par performance."
Jets coach Craig Deans hailed the performance of Goodwin, who delivered remarkably well upfront given his youth.
"He just has the mindset that he is going to be the best footballer on the pitch - no matter which pitch we put him on," Deans said.