Neal Ardley held no punches with his players after their 3-2 defeat to Scunthorpe on Saturday.
Two first half goals form Josh Morris and a second half strike from Ike Ugbo meant Liam Trotter and Kwesi Appiah replies brought nothing more than hope to the home side.
"There was not enough there to win a game of football. We didn't play with any quality," said Ardley.
“I thought for the first 15 minutes we showed real intent and signs of good play, but the mentality when we went 2-0 down was poor.
“I thought for that 20-minute spell after that second goal we went to pieces. That's a fragility in your mentality. That's an anxiety that creeps into the group, you start playing like 11 individuals.”
The result leaves Wimbledon in 16th in League One, two points behind their Scunthorpe.
The Dons had been praised for their early season performances, but Ardley was left seething at their latest showing at the Cherry Red Records stadium.
"I am really angry.
"I am disappointed and frustrated.
“You cannot concede three goals at home," said Neal.
"The staff worked really hard to prepare the boys for the game. We gave the boys everything they needed in as far as they (Scunthorpe) had scored five of their goals in the last four games from set pieces. For an in-swinging free-kick to go straight in the middle of your goal is awful and it's not good enough.
“With the second goal, the last thing I said to the defenders was to solve their counter-attacking. We gave the ball away and within two passes they are one-on-one and through on goal.”
Ardley then went on to lament the ‘sloppy’ third goal ultimately won the game for Scunthorpe, saying: “It’s not good enough.”
The manager says that Tuesday’s Football League Trophy tie against Swansea is a chance for fringe players to stake their claim for a starting jersey going forward.
“We need to be ruthless in our team selection now. You need to earn your place in this team,” said Ardley.
Following the Swansea fixture Wimbledon travel to 10th placed Accrington Stanley on Saturday hoping striker James Hanson is deemed fit following a calf injury.
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