Madrid travel to Italy with a 3-1 lead despite initially falling behind at the Santiago Bernabeu and are firmly expected to progress to the quarter-finals as they look to defend their crown.
But Napoli are not going to make it a comfortable trip and Sarri is hoping that his side play with guts in front of what is sure to be a partisan crowd at Stadio San Paolo.
"It may be that we'll play with a bit of balls," Sarri told reporters at the pre-match media conference.
"The game will be difficult due to the technical qualities that Real Madrid have, plus their great physical qualities. But we're united, now our common goal is to do well.
"The pressure is all on Real Madrid. They are the ones who are world champions and are expected to win. However, our fans are world champions and all of Europe will see that.
"Madrid will probably qualify, they have scored for 46 consecutive games but certainly we will try to make it difficult for them."
Napoli captain Marek Hamsik is also aware of the task facing the Serie A side and has warned his team-mates that, although they need to attack, they cannot shirk their defensive responsibilities.
"We're a team that doesn't control games," Hamsik said.
"We have to go out and attack, but we also have to be careful behind. Napoli are never poor at home in these great matches, so I am sure we will have a great match.
"Real Madrid have great attacking strength and can score goals at any time, but we have to think about doing damage with our patterns of play and those that we have prepared.
"I've played in so many big games, but for me it will be a memorable game. We are trailing and we have to recover.
"It will not be easy, but we have to enjoy and play it as we know how."