Jos Luhukay rued an afternoon to forget as the Owls went down 3-1 to Birmingham at Hillsborough.
Luhukay saw his side reduced to nine men, which made an already tough task almost impossible.
Marco Matias saw red in the first half and Daniel Pudil followed suit after the break.
Luhukay said: “What could go wrong for us did go wrong today.
“We lost an early goal to a mistake, a lack of communication, and then another goal to another mistake.
“But these things will happen in football, players make mistakes and it is unfortunate that we made two early in the game.
“Then we had Marco sent off and from where I was standing it looked a harsh decision but we must respect the decision of the referee.
“They scored again and it made things very hard but we scored through Lucas and this gave us a chance.
“We might have had a penalty when Lucas was tripped and I thought it might have been inside the penalty area but it was given outside.
“Then Daniel takes a second yellow card and if it is a foul then the yellow card and red is the right decision.”
He added: “We now have a week on the training ground before we play Barnsley next Saturday.
“Of course, we must be better and cut out the mistakes we made today because they are uncharacteristic.
“We are stronger than this normally and we must get back to this again.”