Cannavaro criticised the quality of the pitch at the San Paolo, but claimed that despite the missed chance to get closer to Antonio Conte's side, the title race is not yet finished.
"It is a missed opportunity, but the championship isn't over," the Napoli captain told reporters after the game.
"Our real regrets are that we cannot play on a pitch that is worthy of Napoli.
"Sampdoria came here to get a point, but that is fair enough for their situation. We tried, but unfortunately it is difficult against a team that is closed up."
Napoli have confirmed that their pitch will be completely re-laid next week after breaking up badly during the game.