Kozak said that he was pleased with the praise received by manager Paul Lambert, but said that he has not started to show what he is capable of.
"It's definitely a good start as it would have been worse if I had to wait [for my first goal]," Kozak told isport.blesk.cz. "It's fine that I scored but now it's even more important to build on that.
"Coach Lambert praised me after the match but I have to show a lot from my abilities yet. First of all I need to adapt myself because it's a lot different to Italy. I am far from my ideal form.
"But it's going to take some time yet, though I have a good feeling."
Kozak joined Villa on transfer deadline day.