Franck Queudrue has admitted he was to blame for Birmingham's narrow defeat by Manchester United.
The French defender dallied on the edge of his own box at the start of the second half, allowing Cristiano Ronaldo to steal possession and score the only goal of the game.
Steve Bruce's side had enjoyed much the better of the first half but were unable to convert a number of chances and were again frustrated by the resolute United defence after going behind.
Left-back Queudrue told the Birmingham Mail: "I know it is my mistake. But when I went towards the ball but it stuck in the ground. It just stopped.
"So instead of bouncing on, it stayed still and when I put my leg out, it went to him (Ronaldo).
"We put so much effort into the game, I feel very much like s***, I would say, for the guys to get nothing out of it."
The former Fulham and Middlesbrough player knows Birmingham must take their chances when they come up against the leading teams.
He added: "We created some good pieces of play, especially in the first half, but we didn't get any reward.
"That's always the case against the big teams. Sooner or later you get punished, and that's what happened.
"They stopped some things on the goalline and when you don't score, you can get exposed.
"We could have tried all day, but it wouldn't have changed anything."