The Partenopei head coach conceded that his side did not perform well as they slipped to back-to-back Serie A defeats with a 1-0 home loss against Parma on Saturday
Antonio Cassano's 81st minute strike was enough to secure victory for the visitors and condemn the Partenopei to a second successive loss in Serie A after their 3-0 reversal at the hands of Juventus before the international break.
Speaking after the game, Napoli coach Benitez was forced to acknowledged that his team were second best and simply did not meet the standard expected of them.
"I am disappointed, because we did not play to our usual level," the 53-year-old told Sky Sport Italia.
"It's clear that if we don’t play well and our opponents do, then we will struggle. We lost the ball too easily, allowed too much space on the counter and wasted a few opportunities going forward with Gonzalo Higuain and Goran Pandev.
"I don't believe Higuain was too isolated, as Pandev was in a more advanced role. The problem was we didn’t pass the ball properly."
Napoli missed the opportunity to close the gap to Roma at the top of the table to a single point and Benitez refused to blame the international break for their shortcomings.
"All the top teams have to deal with international duty and we knew these things could happen," the former Liverpool and Inter boss added.
"I don't think the side showed a lack of determination or will to win. We have to work harder, but also work well. Naturally when there are two games per week, we don’t have much time, but must analyse what didn't work and try to improve."
Napoli travel to face Borussia Dortmund in the Champions League on Tuesday and may have to do so without Marek Hamsik, who limped off nine minutes after coming on as a second-half substitute for Dries Mertens.
Benitez's men sit second in Group F behind leaders Arsenal and know a win against BVB would strengthen their case for a place in the last 16 of the tournament, but the Spaniard will not be taking any risks with Hamsik.
"We have to wait and see," he said of the Slovakia attacker.
"Hamsik was unlucky to suffer a knock in the same spot where he already had a bruise."