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.”
Chelsea boss Lampard was also left to rue a key penalty incident when he saw Barkley’s late effort clip the top of the bar.
There were confusing scenes moments earlier when it initially looked like Jorginho, who scored for Chelsea in their Super Cup defeat to Liverpool last month, was about to take the penalty.
However, Barkley was insistent and ended up taking the ball after discussions with several of his team-mates including Brazilian captain Cesar Azpilicueta.
“Ross is a penalty taker,” said Lampard. “He scored a couple in pre-season and he was today when he came on and he missed it.
“I don’t know what the conversation was. Jorginho and Willian were the penalty takers on the pitch and when Ross comes on he becomes the penalty taker and he missed it.”
The miss capped a frustrating night for Chelsea, who also saw midfielder Mason Mount forced off with an ankle injury during the first half.
“We probably should have won, or at least got a draw,” added Lampard. “We created enough chances, we had the penalty, and we conceded with their one shot on goal.
“It’s a harsh lesson but that’s Champions League football. We should have got more tonight.”
