On-loan at BVB this season, Alcacer is flying after two seasons of struggles with Barca.
But he insisted: "Trust is key, you can see that everyone is supporting me a lot, all this is the consequence of a lot of work.
"Not at all (does he regret Barca), I have learned a lot in two years, and conclusions are drawn from everything.
"I have shared a lot with (Lionel) Messi. You see things he does in training that others do not do. It's amazing, I have no doubt, the best is Messi."