Coleman believes that the team are capable of much better, but that last night's performance was unacceptable.
He told Sky Sports News: "At times it was men against boys, the goals we conceded were criminal really and the individual errors were disappointing.
"At this level you cannot gift teams goals, you have to at least be hard to beat and play with a bit of pride and we didn't do that. We caved in."
The result follows a loss against Belgium on Friday for the squad, and leaves Wales bottom of World Cup qualifying group A.