The Azzurri won 2-0, putting them clear in second place in Group A, three points ahead of Manchester City.
"We are on the right track, but let's not get big-headed. There are still four difficult games to go," said the Slovak.
This is the 'Group of Death,' so being in this position after facing City and Villarreal is already very impressive.
"It is tough to say whether we'll progress in the competition or not. We were tired in the second half because we all sacrificed ourselves for the team."