While they put up a strong showing at home, a 1-0 loss ensued after Mario Lemina scored from a Jason Steele error.
Post-game, De Zerbi said: "We played well. We made too many mistakes in the first half to score, the last pass.
We created a lot of chances. On the numbers you can't understand how we played well because we didn't shoot many times but we played well to score.
I'm very happy with the performance, the style of play, the attitude and personality we showed. It was very tough playing without width. Nine injured players.
"We have to accept and respect the policy of the club because we finished the game with Baleba, Barco, Benicio, Enciso, we have a lot of young players. Very good young players, the future of Brighton was on the pitch today.
Maybe they are not all so ready to play and to compete for this competition for this level but we are working well and doing great things because we are keeping the same level as last season with a lot, a lot of problems."