Stefano Pioli said that AC Milan should have given themselves more than a one-goal lead in their Champions League quarter-final derby with Napoli after their fellow Italians finished the first leg with 10 men.

Milan had a quarter of an hour to extend their advantage earned from Ismael Bennacer's first-half strike when Andre-Frank Zambo Anguissa was sent off for two quick-fire bookings.

"It's the only regret we have, we should have been more clear-headed," Pioli told reporters.

"It's a shame but they gave a lot. It's a good result after a good performance, let's hope for the next one."

Milan now have to defend a slim lead at the Stadio Maradona in Naples, with the prospect of a semi-final clash with local rivals Inter after they handily won at Benfica on Tuesday.

"It will be difficult match, Napoli are a good team with a lot of quality, the team which up to now had scored the most goals in the Champions League," added Pioli.

"We had a lot of difficult moments tonight... We're expecting Napoli to come at us and we need to put everything out there on the pitch. We won't get our approach wrong... no one here thinks we've already won."

Napoli coach Luciano Spalletti said he would quit if the fans didn't create an intimidating atmosphere for the second leg after tensions between fans and the owner Aurelio De Laurentiis bubbled over in recent weeks.

Protests from hardcore supporters against De Laurentiis over what they believe are his attempts to remove them from the stadium has left home games flatter than one would expect after such a brilliant season for such a passionate fanbase.

Napoli's four-goal home hammering at the hands of Milan in the league earlier this month was played in a bizarre atmosphere, with little chanting and even fights breaking out between home supporters.

"If it happens again for the second leg I will quit. For what we're contending, for the sensitivity these players have because... these players are sensitive to what goes on around them," said Spalletti.

"We played in an atmosphere which did not help us. It's inexplicable not helping the team in that moment."