Home-grown midfielder Angus Thurgate marked his 100th A-League game with a disappointing 2-0 loss to Sydney FC at McDonald Jones Stadium on Sunday to continue the Jets' yo-yo campaign.
After beating Adelaide 1-0 to move back into the top six, the Jets had the chance to jump to third in front of a season-high 8041 fans.
Instead they are again in a logjam.
Two goals in four minutes to Adam Le Fondre (37th) and Robert Mak (41st) turned the match in the visitor's favour.
Thurgate produced a typically wholehearted effort.
A Jets academy graduate, the Port Macquarie junior made his A-League debut as a 17-year-old in a 1-0 win over Brisbane on January 12, 2018.
Jason Hoffman played 13 minutes off the bench for his 196th A-League appearance to join Ben Kantarovski as the Jets' most-capped player.
The Jets pushed and probed but couldn't deliver a killer blow.
Jordan Elsey forced a reflex save from Andrew Redmayne late and Reno Piscopo went close with a long-range effort.
Piscopo was the Jets' most lively but they lacked bite.
The Jets had the visitors in a vice for much of the first half. They employed a high press and pinned the Sky Blues in their own half.
But for all their endeavour and territorial advantage, it failed to translate into domination on the scoreboard.
They had 62 entries into the final third - twice as many as Sydney - but rarely threatened.
Backing up five days after beating Adelaide 1-0 in scorching heat, Papas went with the same XI that did the job at Coopers Stadium.
Co-captain Matt Jurman and Brandon O'Neill returned from injury on the bench, but there was no room for teenage striker Archie Goodwin, who scored a double in the Jets' 2-0 win over the Sky Blues in March.
It was the third straight game that the 18-year-old has been out of the match-day squad.
The clean sheet against Adelaide was the first of the campaign.
Their ability to scramble was tested early by Sydney.
Le Fondre was released down the left and pinged a cross into the box but Dane Ingham did well to get back and clean up.
Max Burgess was dangerous down the right for the visitors and fired a couple of shots in quick succession which were well handled by Jack Duncan.
At the other end, Piscopo was lively but chances were hard to come by in the opening 20 minutes.
The Jets managed to pin Sydney in their own territory midway through the half with a high press.
However, the pressure didn't translate into clear chances on goal.
Piscopo fired a long range effort which Redmayne tipped over the bar in the 34th minute.
A minute later, Sydney were in front.
Anthony Caceres broke the press, released Diego Caballo who dribbled into the box and chipped a cross to the back post for Le Fondre to volley home.
Four minutes later it was 2-0.
From a throw-in, Caceres wiggled towards the by-line and found Robert Mak free inside the box. The Slovakian turned past Angus Thurgate and curled a shot into the right corner.
The Jets have lost all five games this season when they have conceded first.
The start of the second half was similar to the first. The Jets had most of the ball but Redmayne remained untested.
Duncan saved a stinging Burgess effort at the near post in the 63rd minute.
In need of a spark, Papas introduced Brandon O'Neill and Trent Buhagiar.
Jets: Jack Duncan; Dane Ingham, Mark Natta, Jordan Elsey, Carl Jenkinson; Kosta Grozos, Angus Thurgate, Beka Dartsmelia; Jaushua Sotirio, Beka Mikeltadze, Reno Piscopo
Sydney: Andrew Redmayne; Rhyan Grant, James Donachie, Jack Rodwell, Diego Caballo; Paul Retrie, Luke Brattan, Anthony Caceres; Max Burgess, Adam Le Fondre, Robert Mak
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