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.
Maxi Lopez then netted what turned out to be the winner shortly after the interval, with Napoli unable to break down their stubborn visitors in the final stages.
"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."
Next up for Napoli is a home match against Sparta Prague in the UEFA Europa League on Thursday.
