Benitez's side missed the chance to cut the gap to second-placed Roma to four points as Dries Mertens' 32nd-minute penalty was cancelled out by a bizarre own goal from keeper Pepe Reina.
Liverpool loanee Reina somehow allowed Ibrahima Mbaye's weak effort to squirm from his grasp and over the line seven minutes after Mertens' opener.
Napoli, who were without suspended top scorer Gonzalo Higuain, have now won just two of their last seven Serie A games, and Benitez feels they cannot target UEFA Champions League qualification if their below-par performances continue.
"In the first half, the team controlled the game and we should've made more of our domination," the Spaniard told Sky Sport Italia.
"It was a game we should've won and there are regrets.
"I prefer not to talk about the table, but taking it one game at a time. If we don't win games like this, then it's unthinkable to discuss certain placements.
"I am disappointed, with everyone."
Benitez went on to insist Argentina international Higuain's absence was not to blame for the result, instead hinting that a lack of effort may have cost Napoli.
"We do not depend on Gonzalo," Benitez added. "But we do depend on determination."
