Napoli had snatched all three points with a dramatic stoppage-time winner in a 2-1 success at Genoa on the opening weekend, but they failed to build on that victory as Chievo left the Stadio San Paolo with a maximum return for their efforts.
It could have been a different story for the hosts had Gonzalo Higuain not seen a first-half penalty saved by Francesco Bardi.
"It is difficult to explain this defeat," Benitez told Sky Sport Italia.
"Towards the last 20 minutes we got a little too hasty and wasted opportunities. It's one of those games where if it had ended 3-1, nobody would've complained.
"The fans were fantastic with the team and did what they had to all the way to the end. If we do not score a goal, then we cannot complain.
"We have to make more of our chances and win a game like this.
"It is a problem if the team doesn't create chances, but with a penalty, 11 clear chances and 33 shots, that changes everything.
"If we had been 3-0 up at half-time, nobody could've complained."
