Roy Keane felt Town were worth at least a point against Barnsley after seeing his side go down to a last minute winner from Jon Macken.
Former Blues' loanee Macken struck in added on time after Liam Rosenior had cancelled out Iain Hume's opener.
Hume also missed a penalty for the Tykes and Roy was angered by both that decision and a free-kick that led to the winner.
"I couldn't understand what the penalty was given for," said the Town boss. "None of their players appealed for it and I didn't agree with the free-kick against Tommy Smith that led to their second goal.
"He's won the header and then they have taken the kick 10 yards further forward. That said we should have dealt with it. A minute before that, we had one kicked off the line and you go from almost winning it to losing in with the last kick of the game.
"We had the better of the chances and deserved more than we got but that's the way it's going for us at the moment."