The Middlesbrough manager could have been orgiven for assuming victory over Swansea City was assured after his side raced into a 3-1 lead at the Riverside.
But goals from Scott Sinclair, Ashley Williams and Craig Beattie added to the first half strike of Nathan Dyer to give the Swans the win that they so desperately needed after the disappointment of last Sunday.
"There are a million excuses, but the bottom line is we didn't defend well enough." Mowbray said after the game
"It's a much-changed defence – a few weeks ago we had Wheater and Bates, Hoyte and Bennett. I'm not trying to make excuses, it's just the way it is.
"They're young players who will hopefully feel the pain from today and learn from it and understand the concentration and decision making needed to play at this level.
"We made some bad decisions and the penalty gave them back a bit of belief and impetus. We went into the game with a game-plan and the game-plan worked all right.
"We managed to cope with their expansive game, but the nature of the way we lost our goals was disappointing and frustrating for us.
"I don't think they really carved us open and they weren't particularly good goals from their point of view. It was more us shooting ourselves in the foot with some bad decisions. At 3-1 the game should be comfortably seen out."