The Granata were hoping for a fourth consecutive victory, but were held to a goalless draw at the Stadio Bentegodi.
“We weren't bad in terms of performance, but it's never easy to score against Chievo, as Napoli proved last week," Mazzarri told Sky Sport Italia.
“We had two particularly good chances, but in order to win games, you need to score goals. It's a pity for the fans, as we wanted to give them a fourth straight victory.
“I have regrets about this game, to be honest, as I hoped we would get all three points here."