City quickly took a two-goal advantage in the Champions League clash with strikes from Raheem Sterling and Gabriel Jesus in the opening 13 minutes but were left holding on for the win when Amadou Diawara pulled a goal back from the penalty spot.

Former Barcelona and Bayern Munich manager Guardiola said his team tired but that he was proud of his players for holding on for a win to maintain their 100 percent record in Group F.

"I did expect the game to go to 90 minutes because Napoli are an exceptional team," Guardiola told a news conference. "We made a good first half, for 30, 35 minutes, we created the two goals and could have had a third or fourth goal. After that we were tired and couldn't finish our little counter-attacks, we didn't finish the actions.

"They have a big ability to make short passes. It is one of best teams I ever faced as a professional. That is why I am so proud because you cannot beat Napoli unless you produce a good performance."

Despite losing two of their three games in the Champions League, Napoli have made a perfect start to Serie A with eight wins out of eight. And Guardiola believes they have the quality to break Juventus's six-year strangehold on the Italian title.

"I knew before we played and I know now -- they are one of the best teams in Europe at the moment," he added. "It's one of the wins I'm most proud of in my whole career. Napoli, for the way they play, of course they can win the league."

Napoli boss Maurizio Sarri was equally complimentary of Guardiola's side and believes City are among the favourites to win the Champions League. However, he admitted they were left ruing missed opportunities -- particularly Dries Mertens' first half penalty miss.

"We managed to fight back and not many teams at the moment are able to come back in the way we did and cause difficulties for Man City," the Napoli boss said. "We regret fact we missed the first penalty, but we know now that we are on the right path to be competitive in Europe as well.

"I've seen a huge step forward compared with the match in Real Madrid last year when we were lucky enough to score first. Here we had to come back into the game from a very difficult situation after the first 25 minutes. I think we've definitely taken a step forward.

"Our opponents were very strong and made it tough for us. I think City are serious contenders. They have an extraordinary team with extremely positive qualities -- they are quick, they are tactically savvy. If they can maintain their physical and mental shape as they are now they can really go all the way."

City maintain their 100 percent start in this season's Champions League and City defender John Stones was pleased by several aspects of their performance.

"We've put ourselves in a good position, a lot of games to play still. I say it all the time but we've got to keep going game by game," he told BT Sport 3.

"I think tonight was a great test to see where we were really at after a good run of hard games. We knew it was going to be a tough test.

"We wanted to play our game and I think some of the football out from the back right the way through to the guys up top was, at times, great to watch for me personally.

"We're a bit upset to concede the goal that we did, I thought it was a bit soft but overall: a great team performance. Every game is a hard game. We want to keep improving, keep scoring goals, keeping clean sheets and hopefully we can progress in the group.''

Fellow defender Kyle Walker was quick to hail the performance of Ederson after City sealed a 10th consecutive win in all competitions.

The former Tottenham full-back said: "We always knew they were going to come at us in the second half. I thought the lads showed good character out there. Ederson's kept us in it and we need to say a big thanks to him.''