Melbourne Victory suffered a 4-2 loss to PlayStation 4 NPL2 West leader Northcote City on Saturday.
After Alec Goodwin and Baggio Yousif put Northcote 2-0 up, Victory fought back and was level thanks to Nicholas Sette and Pierce Waring.
But second-half headers from Tomislav Fadljevic and Matthew Whatley secured Northcote's win at John Cain Memorial Park.
Victory head coach Gareth Naven said he was satisfied with the performance, but lamented his side's set-piece defending.
"It's bitter sweet, to be honest," he said.
"We've got (Aaron) Anderson (16), Sette (17), (Brandon) Lauton (17), (Joshua) Kelic (17), but it's what they need to deal with.
"We need to be more disciplined in our approach to achieve something. We're doing a lot of good things, but need to be more consistent with those good things and I just believe they're working very hard, which is a good character trait.
"From 2-0 down, 2-2, it's good for the boys to achieve that and very happy for them in that situation.
"Obviously two set-pieces, they are our Achilles' heel. I think in youth football dealing with set-pieces is a challenge and the best way to deal with that is prevent it, don't let them happen, work really hard to stop crosses, work really hard to not give free-kicks away, work really hard to make sure you don't give corners away.
"Then, when you actually do defend it, be brutal with it, to be honest, and it's hard to get 16-, 17-year-olds to be brutal in their defending, but they're starting to head towards that."
Victory, which had a squad of mostly 17-year-olds, made a slow start and fell 2-0 behind inside 22 minutes.
Goodwin tapped in the opener after a sloppy giveaway before another turnover of possession led to Yousif's goal.
But the visitors responded to falling behind and were level by half-time.
Sette volleyed in from inside the area to pull one back after Northcote was unable to deal with a set-piece from Joshua Kelic.
Waring equalised with eight minutes remaining in the half, the forward drilling a brilliant finish into the bottom corner for his ninth of the season.
Victory was put under heavy pressure to start the second half, and it conceded twice in three minutes.
Fadljevic headed in a corner at the back post before Whatley also scored with a header after Victory failed to clear.
Earlier, Victory's under-20s went down to Northcote City 5-2.
Victory is back at home next week, hosting Moreland Zebras at Epping Stadium on Saturday, June 10.
PlayStation 4 NPL2 West 2017 Round 17
Northcote City 4 (Alec Goodwin 19', Baggio Yousif 22', Tomislav Fadljevic 64', Matthew Whatley 66')
Melbourne Victory 2 (Nicholas Sette 26', Pierce Waring 37')