- Tag results for Napoli
Ivorian Christian Kouame had shocked Carlo Ancelotti's side by opening the scoring after 20 minutes in a match which was suspended for 13 minutes around the hour mark because of torrential rain.
Buffon was suspended for PSG's opening three European games for his behaviour and comments towards the referee during Juventus' quarter-final loss to Real Madrid last April.
Napoli, with 25 points from 11 games, move three points behind champions Juventus who host Cagliari on Saturday with Inter Milan a further three points back before their game against Genoa.
Coach Massimiliano Allegri is likely to rotate his squad after Manchester but he will still be unable to call on Sami Khedira, Emre Can and Mario Mandzukic.
PSG are third, a point behind Napoli with a trip to Italy up next before Liverpool visit Paris next month.
The Italian is returning to the Parc des Princes for the first time since his Bayern side were comprehensively beaten 3-0 by PSG in the group stage of last season's Champions League.
AC Milan extended their unbeaten run to eight matches in all competitions as Gonzalo Higuain scored twice in a 3-1 victory over lowly Chievo at the San Siro.
Portuguese superstar Cristiano Ronaldo played a role in all three goals as Massimiliano Allegri's side ensured a maximum 21 points after seven games.
Ancelotti's side are three points behind Juventus who have a 100 percent record after six games.
Lorenzo Insigne rattled the crossbar in the first half for Napoli, while Red Star defender Milan Rodic made a vital goal-line clearance to deny Jose Callejon in the Group C encounter.
But while Ronaldo's chance of finally grabbing his first goal in Italian football is increased by his Juventus side hosting Sassuolo this weekend, Napoli faces another tricky test — against Fiorentina
Vlad Chiriches is set to undergo surgery Monday but the club did not give an estimate for how long his recovery was expected to take.
Sarri had two years left on his contract after leading his hometown club Napoli to challenge champions Juventus for the title last season.
Juve have now won their opening two games after last weekend's 3-2 success against Chievo in Verona.
Mohamed Salah, who hit 32 Premier League goals last term -- a record for a 38-game season, added a third for Jurgen Klopp's men just before the hour.