Liverpool boss Jurgen Klopp and Chelsea manager Frank Lampard were both left to reflect on key penalty incidents as they began their Champions League campaigns with defeats.
Ross Barkley missed a late chance to equalise for Chelsea from the spot as they lost 1-0 at home to Valencia.
Meanwhile, Napoli’s first goal in their 2-0 win over holders Liverpool came from a dubious spot-kick.
“For me it’s clear and obvious, no penalty,” said Klopp.
German referee Felix Brych pointed to the spot with eight minutes left when Andy Robertson was judged to have fouled Jose Callejon.
Dries Mertens converted the spot-kick before former Tottenham striker Fernando Llorente sealed the win with a second goal in stoppage-time.
“Callejon jumps before he has any contact,” added Klopp. “But we cannot change that so we have to be critical with ourselves.
“We did well in a lot of moments, we played a lot of good football but we didn’t finish off.”
‘I don’t know what the conversation was’