Napoli’s unexpected loss means Juventus is only two wins away from clinching a record-extending eighth straight Serie A title.
Injury-depleted Napoli was beaten 2-1 at relegation-threatened Empoli on Wednesday.
Juventus, which won 2-0 at Cagliari on Tuesday, leads Napoli by 18 points with eight rounds remaining and the Bianconeri hold the tiebreaker, too.
If Juventus beats AC Milan on Saturday and Napoli lose again to Genoa a day later, Juventus could clinch the title this weekend.
Napoli, which visits Arsenal in the Europa League quarterfinals next week, has a long list of injured players: Lorenzo Insigne, Faouzi Ghoulam, David Ospina, Amadou Diawara, Raul Albiol and Vlad Chiriches.
Empoli, which also played well in a 1-0 loss to Juventus at the weekend, went ahead when a deflected shot from Diego Farias confused goalkeeper Alex Meret.
Piotr Zielinski equalized with a long-range blast before the break and didn’t celebrate — as promised — against his former club.
An uncharacteristic defensive lapse contributed to Empoli’s winner, as Giovanni Di Lorenzo was left unmarked to head in from a corner.
Empoli could have had another but Meret did well to rush forward and deny Farias on a counterattack.
Empoli moved one point above the drop zone.