Raul Albiol scored two minutes from time to secure a point for the Partenopei, and Benitez was particularly critical of Gonzalo Higuain and Dries Mertens, both of whom missed chances to find the back of the net.
"It (Higuain's opportunity) looked easy, but replays showed it wasn't that simple, as it was a very tricky angle. He still should have done better, though," he told reporters.
"We haven't been ruthless enough in attack recently and if Dries Mertens had scored instead of hitting the post, it would have been a different game.
"We needed a bit more speed in moving the ball, but hitting the woodwork three times against a team that came to defend was very unlucky."
Napoli are currently third in the Serie A Serie A table, 12 points behind league leaders Juventus.