But Klopp will know his side needs to improve, in particular away from home, as there are only so many magical nights it will be able to conjure up at Anfield.
“First half we played some good stuff,” captain Jordan Henderson told BT Sport. “Just that last bit we were missing today. At home Napoli are a good side and they’re going to create some chances.
“The mistakes for the goals we need to improve on, overall we can be better of course and we’ll take responsibility and move forward.”
In the first half, Napoli was by far the better side and had the ball in the net early on.
The Stadio San Paolo, Napoli’s famed crumbling colosseum, erupted as Mertens headed home from Adrian’s save, only to fall quiet after seeing the linesman’s flag raised for an obvious offside.
Coach Carlo Ancelotti will have been delighted with the intensity shown by his side on a sweltering night in Naples.
The second half was far more even and Liverpool did eventually get a foothold in the game to begin dominating.
The pace of Mo Salah and Sadio Mane was also proving to be a headache for Napoli on the counterattack, with the Senegalese forward squandering a glorious opportunity to play his teammate in on goal.
Alex Meret brilliantly tipped away a Salah shot, though that save was arguably bettered by one from Adrian, who somehow clawed the ball away from his goal to deny Mertens.
Eventually, Napoli’s breakthrough came somewhat against the run of play, as Andy Robertson dangled out a tired leg that Jose Callejon obligingly fell over.
On second viewing, it looked as though the Spaniard rather jumped to the ground but VAR deemed the referee had not made a “clear and obvious error” so didn’t overturn the decision. “I saw it now and for me I thought it was clear and obvious not a penalty,” Klopp told BT Sport. “Because Callejon jumps before there was any contact.
“There were opportunities, this was a much better game than we played away last season and lost in the last minute.