The Serie A side would have progressed to the knockout stages had they and Group B rivals Benfica both won on Wednesday, but the Portuguese outfit blew a three-goal lead to draw 3-3 before the later game kicked off at San Paolo.
And after seeing his Napoli team booed by their supporters at the end of a goalless stalemate, Sarri admitted that the group's other result was to blame as no result could guarantee qualification.
"We went out for the warm-up with Benfica winning 3-1, and then the news came that it was 3-3," he told Mediaset Premium.
"The boys realised that a win or a draw would not give us anything more. This has negatively affected us.
"Up to a quarter of an hour from the beginning [of the match], there was great desire to win. It is difficult not to be influenced by anything."
Benfica top Group B ahead of their final game against Napoli, who are level on points with eight apiece.