The Serie A leaders must overturn a 3-1 deficit when they play in Germany on Thursday, but coach Sarri fears his players may be affected by the fans' lack of appetite for continental success, with a first Scudetto since Diego Maradona's time in Naples on the cards.
Sarri rested a host of key players as a sparsely populated San Paolo watched Napoli fall to a deserved defeat against the Bundesliga side last week.
But the 59-year-old still retains hope of going through at the Red Bull Arena, as long as his players sharpen up.
"We played like buffoons in the first leg and 70 per cent of that is my fault, 10 per cent the club, 10 per cent the players and 10 per cent the staff," said Sarri.
"It certainly wasn't the fault of the reserve players, because we had our worst part of the performance when the first-choice players came on.
"We must step on to the field with the desire to win and prove ourselves. Hopefully the incidents can go our way, so we can have a shot at qualification.
"Last Thursday's performance was a bolt from the blue for me as well. At the San Paolo, we simply weren't able to recharge our batteries after the Serie A match. At the moment we are a little short-staffed too, so that doesn't help.
#Sarri : "We'll do everything in our power to give our fans something to celebrate. They're focused on @SerieA_TIM but it's our job to draw their attention to the @EuropaLeague "— Official SSC Napoli (@en_sscnapoli) February 21, 2018
"However, it's obvious the team is playing with heart and determination in Serie A, whereas we can't do that in other competitions. It's a step up this team must make, probably once we increase the squad and are more able to handle several different tournaments.
"I don't think the fans are divided, as they are focused on Serie A because Napoli haven't won it in 30 years, but we mustn't be influenced by what the fans want. We must push the fans forward and charge them up. I will admit, right now our fans are only interested in the Scudetto."