Guy Whittingham believes Dan Butler will have had a sleepless night over his costly Leyton Orient mistake.
But the Blues boss has promised the teenager will not be dropped for Saturday’s trip to Doncaster.
Butler’s under-hit backpass on 57 minutes gifted Shaun Batt the only goal of the game at Matchroom Stadium.
It was an error of judgement which undermined an otherwise highly-encouraging display on a cold, cold night.
Butler was substituted 20 minutes later in a tactical change – with Ashley Harris introduced to give more attacking impetus.
But Whittingham has every faith in the 18-year-old’s ability and will continue to pick him as first-choice left-back.
He said: ‘It was a simple mistake from Dan. He has gone for the backpass, under-hit it and Batt has gone through and has given Eastie no chance.
‘Apart from that he had done well. He was competing well and covering well, which is what makes it disappointing.
‘I don’t think he would have slept last night.
‘It’s one of those things, as a defender you make a mistake and it costs you a game.
‘As a striker I made mistakes and I didn’t sleep all night thinking about the goal I should have scored.
‘I remember I once had a quarter-final against Wimbledon, had a one-v-one with the keeper and missed it – and we lost 2-1 in the end.
‘You think if I had put that in we would have been 1-0 up and you don’t sleep.
‘Dan probably didn’t sleep last night and maybe tonight – but he will be back in the side on Saturday, you can be rest assured of that.’
Butler has established himself as a regular at left-back since being recalled from the Hawks at the turn of the year.
Since then he has made 12 appearances – in addition to his Capital One Cup debut at the start of the season.
Whittingham has made no secret of his desire to tie Butler to the club beyond this summer when his existing deal expires.
That is recognition of his encouraging displays – and the caretaker boss was impressed how last night he dealt with his mistake.
He added: ‘Fair play to Dan, it (the mistake) didn’t go to him.
‘He could quite easily have crumbled as an 18-year-old.
‘But he carried on. We weren’t going to bring him off, the only reason we did was to change shape a little bit and try to get Ashley Harris in the middle there to cause problems and he did.’