Neal Maupay - who was guilty of one of the misses of the season in the reverse fixture - opened the scoring for the Bees after only five minutes, but a stunning volley from Sol Bamba levelled things up before Callum Paterson gave the visitors the lead in first-half stoppage time.
"We started the game extremely well, probably should have scored in the first minute and the keeper has made a good save. Then Neal goes through one on one and probably exorcises a few demons by scoring that goal. We were excellent for the first 20 minutes. The only danger was I thought we left the back door open a little bit too often," he told reporters at his post-match press conference.
"Daniel Bentley had to make a couple of saves from turnovers, and they've got a little bit of pace they can break with. They scored the goal from a corner, it's a hell of a finish, and if we go in at 1-1 I think with a few tweaks at half time we go on and win the game. Unfortunately we made the mistake just before half time and that was a bit of a kick in the teeth.
"Just before the third goal we go through and their lad gets a great block on Ollie Watkins and it just goes onto the top of the net rather than inside. I think that was the story of the night. I thought we had a game plan and it was working. We knew they would go man for man with us and we felt that if Neal came a little bit shorter it would create a hole in behind, and we used that a number of times.
"Sergi [Canos] gets brought down right on the edge of the box when he's about to go through, Ollie's had a chance. On another day the scoreline might be different, but unfortunately it's a game of fine margins and we ended up on the other side of that margin today.
"[The players] will be deflated because it's a game we felt we could have won. Even at half time, going in at 1-2, we always felt that second half we could go and score more goals. But you also have to give credit to them. They threw their bodies on the line at times when they needed to, and we probably just lacked that little bit of quality."
Brentford have now lost back-to-back games in the Championship, leaving them eight points adrift of the playoff places.