Melbourne Victory suffered a 3-1 loss to Springvale White Eagles in the PlayStation 4 NPL2 West on Saturday.
Callum Goulding's second-half penalty had drawn Victory level after Isaiah Joseph's opener at Epping Stadium.
But a controversial Boima Karpeh goal put the White Eagles ahead before the striker sealed the win deep in additional time.
Victory head coach Gareth Naven said his team's execution was below where it needed to be.
"Generally, our players are doing their best. You can tell in their faces, their expression, their endeavour," he said.
"I'm a person who's asking more and more from them and they're doing their best to try and satisfy that. It's a continual work in progress and a standard and a focus that the bar is set high.
"I think as a playing group, they're aware of that and maybe it's not new, but I'm challenging the players to adapt, to be better strategically, manage the game, manage the match, tactically understand different situations, make decisions right or wrong and there's definitely a lot of overload at the moment which hopefully helps the learning process as well.
"I'm disappointed because our ability needs to be at a level where if we've got possession of the ball with no pressure or no incumbent amount of pressure around us, we must be able to pass the ball to a blue shirt.
"We must be able to execute with no pressure and that habit of behaviour is delivered within a training session and that habit of behaviour I'm asking of the players is of a high level, it's non-negotiable, especially when there are no decisions to make. It's executing a pass from A to B. This is what we're trying to get our players to understand.
"High standards are required and expectations on yourself, individually and collectively, to achieve those things and there's nothing wrong with having those standards.
"It puts people in a better place to achieve it at the next level because if they're not doing it here, you can't achieve it at the next level or it's going to be very difficult to achieve it."
Following a scrappy start, the visitor took a 14th-minute lead when Joseph tapped in at the back post after Victory was unable to deal with a cross.
Karpeh had a header ruled out for Springvale before Victory forward Nuh Sehavdic went close twice.
The 17-year-old shot across the face after a Brandon Lauton pass before striking the outside of the post having been put through by Nicholas Sette.
Victory was much improved after the break and levelled in the 56th minute.
Goulding clinically dispatched a penalty into the bottom corner after Brandon Jansz was brought down following a run down the left.
The host looked the more likely to find a winner before Karpeh's controversial goal.
Handball was paid after Victory took a throw-in which had been awarded, with Karpeh heading in the free-kick at the near post.
Karpeh sealed the win in additional time with a side-footed finish.
Earlier, Victory's league-leading under-20s recorded an entertaining 3-2 win over Springvale White Eagles.
Victory is next in action with a clash at home to Box Hill United at Epping Stadium on Saturday, July 8.
PlayStation 4 NPL2 West 2017 Round 21
Melbourne Victory 1 (Callum Goulding 56' pen)
Springvale White Eagles 3 (Isaiah Joseph 14', Boima Karpeh 87'/90+5')