The Zebrette had the lead through Hassane Kamara before Mario Pasalic and an Udinese own goal saw Atalanta through.
Afterwards, Gasperini said: "We were out of step, both in defending and in finding references. Up front we moved well, defended badly and played worse. In the second half there was another match, managing to change the plan and get back into the game is never easy, we played a very good quarter of an hour.
"We were more precise, we enhanced the offensive department, then in the final we controlled without many risks. With the full squad we showed that we can play with continuity and value."
On the performances of Odilon Kossounou and Raoul Bellanova, he added: "Kossounou is convincing us more and more, I think he is a player who will quickly become an important cornerstone. He is a boy who knows football, it is not just physical strength. Bellanova is much more effective when there is the possibility of playing against teams that open up a bit, today he gave the right energy."