Zeman insisted he was "happy with the performance".
"It is a step backwards in terms of result, but the team tried to play and put the opposition under pressure," he said of the 4-1 defeat.
"Of course goals count in football, we didn't score them and Napoli did. I am generally happy with the performance, though.
"We defend zonally on set plays and clearly got something wrong on Edinson Cavani's goal. We conceded there, it happens."
Mattia Destro wasted several chances before he was replaced by Pablo Daniel Osvaldo.
"If Destro did not score, then it means he was hasty. I am satisfied with his performance too, as he put himself forward and created some opportunities. He moved well and it's a shame he didn't finish them off, as a striker lives for the goal. He has quality and we have faith in him."