"It was probably 20 or 30 seconds of us not doing what we wanted to do which cost us.
"You can't give Charlie Austin two inches. We said before the game that we'd have to mark him because he's a unique goalscorer at this level. Then Martin Cranie doesn't have to tackle him there.
"We defended well as a team and limited them to two chances in the first half. We kept them at bay and kept their fans low, but that first goal really gave them energy and verve.
"There were a few tired performances in the last 20 minutes. We just ran out of legs.
"We've got to balance and shape this squad and find out who we're going forward with. It's two weeks to assess things."
David was talking to BBC Radio Sheffield.