Louis Lancaster said poor defending cost his side as they went down 3-0 to Cardiff City's Youth Team.
Cardiff had the better of the game but Louis was disappointed with the mistakes that gifted the Welsh side their goals.
The result now leaves the Bees winless after their opening three games.
Speaking exclusively to Bees Player after the game Louis said: "The performance was patchy. It was good in parts but then in other parts it wasn't.
"But the goals were just mistakes, basic mistakes, which have cost us today."
"We did come into the game a bit more after the first half-hour but from the side-line there is only so many things I can get across to the players.
"The line was too deep so I tried to squeeze them up so we could have a bit more of a pressing game as they were having the ball at the back and we did get a bit of success from that.
"Obviously the second half we conceded one goal but such a silly goal to give away. However apart from that it was 0-0. We created more chances and stopped them scoring so it was better.
The Youth Team stayed overnight in Cardiff before the game and something which Louis thinks will help to aid their development as footballers.
Louis said: "Staying overnight was great for the players. With an 11 o’clock kick off we could leave at six in the morning but we chose to get the lads in in the afternoon yesterday we have a good training session which was positive, fed them, got the coach up here which is all part of the experience.
"If they play first team football that is what is going to happen then so it is great for them."
Bees Player subscribers can here the full interview here