The Vatreni head into Monday's decisive Group A clash on the back of a 4-0 victory against Cameroon which saw Mandzukic return from suspension with a brace.
"I felt good," the Bayern Munich striker is quoted as saying by ESPN following the game in Manuas. "I was well-prepared because I got some extra training after missing the first game.
"The whole team worked as well. We are all happy but there is still room for improvement and progress of course. The goals came as a reward, but all I think about is to win."
Cameroon have exited the World Cup following the defeat.