The hosts dominated possession at the Stadio Diego Armando Maradona but lacked sharpness in front of goal, missing the creativity of injured playmaker Kevin De Bruyne. Eljif Elmas drew an early save from Michael Zetterer before Scott McTominay headed wide, while Frank Anguissa fired over from distance.
Frankfurt offered little threat in the first half, yet remained dangerous on the counter after the break. Mario Gotze's header and Ansgar Knauff's close-range effort forced solid stops from Vanja Milinkovic-Savic, while at the other end McTominay squandered two golden chances-taking a heavy touch when through on goal, then blazing over from six yards after Anguissa's cutback.
Napoli pushed hard late on, with Giovanni Di Lorenzo and Rasmus Hojlund both denied by Zetterer, but a breakthrough never came. The draw marked their second straight goalless home game and the first time since 2016 they have failed to score in a Champions League fixture in Naples.
Conte's side stay winless in Europe since beating Sporting, while Frankfurt's discipline earned them a valuable away point.
Chelsea head coach Enzo Maresca is hopeful that playmaker Cole Palmer will recover from a groin injury in time to face Barcelona in the Champions League later this month, followed by a crucial Premier League meeting with Arsenal.
Bayern Munich handed Paris Saint-Germain their first defeat of the Champions League campaign, winning 2–1 at the Parc des Princes to extend their perfect start to 16 victories in all competitions.
Liverpool recorded an impressive 1-0 win over Spanish giants Real Madrid in the Champions League on Tuesday night.
Arsenal striker Viktor Gyokeres has been ruled out of Tuesday night's Champions League clash against Slavia Prague.
