He said: "It is important that you defend properly, especially from set-pieces but we didn't do that. I don't think the scoreline reflected the game but we paid for our mistakes.
"I thought Louis was a little bit unlucky. I won't argue with the decision but there were a few tackles that could have resulted in a booking. His bookings were a bit harsh."
Meanwhile,City's U18 side were beaten at Crystal Palace. Aaron Stringfellow netted for Steve Ogrizovic's side in a 2-1 defeat.