The 0-0 scoreline on Wednesday saw Juventus overtake Napoli at the top of the table and, with the champions playing at lowly Palermo in Saturday's early kickoff, Napoli will not want to concede any more ground.
Unsung Chievo, level on points with AS Roma and Inter Milan in third place, are on form and just one point behind Napoli ahead of a match that will be a real benchmark of their ambitions.
Napoli and Juventus, who thrashed Cagliari 4-0 in Turin on Wednesday, are the favourites in week six but with Roma -- at Torino on Sunday -- and Inter (home to Bologna) in striking distance.
Inter's Mauro Icardi in particular will be looking to continue the run of form that has taken him to the top of the scorers' standings with six goals.
Sarri felt his side should have had two penalties against Genoa, after dominating the match, and it was not the first time the decisions had gone against Napoli.
Team captain Marek Hamsik, who hit the bar, agreed but added that they needed to keep their focus.
"We are just thinking about playing football and not arguing," he said. "We're strong, you can see that from our results and the way we play. If we keep on this path, we'll go a long way.
"This season is going to be more closely fought than the last one. (Gonzalo) Higuain's departure was a big blow, but we're united and are a great group."
Argentina striker Higuain, who left Napoli for Juventus in July in a 90 million euro deal after scoring a record 36 goals in 35 games for the Serie A runners-up, was on target again on Wednesday.
AC Milan, three points off the lead but sixth overall, travel to ninth-placed Fiorentina in Sunday's late match while Lazio host Empoli.
Bottom sides Crotone and Atalanta Bergamo play in the south on Monday, when Cagliari also host Sampdoria.
(Reporting by Alan Baldwin, editing by Toby Davis)
