MILAN (AP) — The past week was penciled in as a test of Napoli's credentials at home and abroad.

So far, those credentials have impressed.

Last Saturday, Napoli won at title rival Roma 1-0 to stay atop of Serie A and remain the only perfect team with eight wins after eight rounds.

Then on Tuesday, Napoli met Manchester City in the Champions League. Apart from a terrible start which saw it concede two early goals, Napoli proved stoic in a 2-1 loss to one Europe's best sides.

"We have faced one of the best teams of my career, probably the best," said City manager Pep Guardiola, who previously coached Barcelona and Bayern Munich.

Napoli forward Dries Mertens boasted: "If we play our football we can compete against any team."

Next up this Saturday is Inter Milan, the only other unbeaten team in Serie A. Inter is second in the league, two points behind the southern Italian side.

The scheduling has been criticized by furious Napoli coach Maurizio Sarri.

"Someone misunderstood the criteria for the drawing up of the fixture list," Sarri said. "We represented Italy in one of the most important stadiums in Europe, against a squad which I believe is the strongest of them all. We did that three days after a direct match against Roma and three days before that against Inter.

"Evidently, at the moment in the league there are people who are unsuitable for doing certain things (scheduling)."

Napoli is sweating on the fitness of key player Lorenzo Insigne, who limped off against City with a thigh strain. His condition is being evaluated daily and he remains a doubt.

Insigne has started all 13 of Napoli's matches this season as well as Italy's four World Cup qualifying matches.

Algeria international Adam Ounas could get his first start, or Piotr Zielinski could move to the left as he did in Manchester, where midfielder Allan replaced Insigne.

Whoever starts will be full of confidence after the manner of the midweek defeat. Sarri believes so.

"City is a devastating side, it has scored 17 goals at home, so us putting them under pressure in the second half is a significant result for us in terms of conviction," Sarri said.

"We were really good in managing to come back and that's something we must bear in mind in future. As I said, holding our own against City for an hour is a great sign. We must push on from here and continue on our path."

Napoli has been sweeping all before it in Italy with a devastating attack, complemented by quickfire passing. The victory in Rome was the first league match this season in which Napoli didn't score at least three goals.

But Inter has a solid defense, having let in just five goals all season — the joint lowest in the league, along with Napoli and Roma.

It also has fearsome counterattacks, often led by Antonio Candreva and Ivan Perisic and finished off by Mauro Icardi, who netted a hat trick in the 3-2 derby victory over AC Milan last Sunday. Icardi has nine goals in eight Serie A matches.

Inter has a lot of motivation and has title credentials to prove, too. It hasn't won in Naples in 20 years.