The 1-0 loss at the Stadio Ennio Tardini, combined with second-placed Roma's 3-1 win at Cagliari, means Napoli are now 12 points adrift of the Eternal City club with only six games go.
Napoli's chances of overhauling Roma may now be over, but Benitez will not accept his side letting their standards slip over the final weeks of the season as they look to assure themselves of the final Champions League spot.
Benitez will also hope to continue working on some of the weaknesses in his side, something he feels is not an overnight job.
"We are obviously disappointed," Benitez said on the club's official website, www.sscnapoli.it. "We can do better.
"We are clearly missing something that only with time and growth we will be able to achieve.
"We have a good quality side that has its strengths and its weaknesses.
"We need to improve on our weaknesses, something we failed to do against Parma.
"Now we just have to work hard and try to do as best as we can in the final stretch of the season."
Napoli, who are nine points clear of fourth-placed Fiorentina, host Lazio on Sunday.