Paolo de Ceglie struck both goals for the Ducali.
"Clearly 2-0 makes everything look bad. It's true we didn't put in the performance we wanted and conceded a goal at the first cross, which then made us lose confidence and get tense," Mazzarri told Sky Sport Italia.
"Parma were vehement and we only created one chance in the first half. We hit the post with Kovacic and had a great chance with Palacio, but lately we've been struggling to score goals. We were also tired, as the same players have to keep going.
"I heard criticism of Higuain, who also came from the World Cup Final and took a while to get into gear. On top of that, Palacio had a serious injury and his ankle is still not in good shape.
"Today we were forced to use Hernanes and I don't know whether he injured himself again. We are in a difficult situation in terms of injuries. Even in the emergency, we played the last three games pretty well, but again we failed that extra step. It was the same team that beat Sampdoria, but looking at the bench I didn't exactly have many alternatives."
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