Guardiola's men appeared on course for another of the demolition jobs they have made their calling card in the Premier League this term but Napoli thrillingly rallied, pulling a goal back through Amadou Diawara's second-half penalty after Dries Mertens had an earlier spot-kick saved by Ederson.
City held out in a tense finale but the memory of their opening salvo remained fresh in Sarri's mind as he told a post-match news conference the English club can shake off their previous missteps in Europe to challenge the continent's heavyweights.
"It is a great team," Sarri said of Manchester City. "It has everything.
"They are very quick, they are tactically very savvy and, if they stay in the kind of good mental and physical shape they are now, they really could go all the way."
Guardiola was arguably even more gushing as he labelled Napoli "one of the best sides I faced in my career, probably the best".
"That is a good question for Maurizio Sarri," he said when asked if Sarri's vibrant team can scoop the Scudetto. "I don't know.
"I know Maurizio Sarri has a lot of respect for Juventus but if Napoli don't have too many injuries, with the way they play, of course they can win the league."
In an impassioned post-match performance, Guardiola dedicated City's victory to Catalan politicians Jordi Sanchez and Jordi Cuixart, who have been arrested on sedition charges.
"We have shown in Catalonia that citizenship is bigger than any ideas," he added. "We hope they will be released soon."