A last-gasp goal by Empoli midfielder Viktor Kovalenko condemned champions Napoli to a 1-0 home loss in Serie A on Sunday as they squandered the chance to move up to third in the standings.
Ukrainian Kovalenko scored the winner in stoppage time, netting from inside the box as the ball bounced in off the far post.
Napoli, who were still without injured striker Victor Osimhen, thought they had moved in front through Giovanni Simeone in the 27th minute, only to see his goal ruled out for offside.
Napoli, who stumbled to a 1-1 draw at Union Berlin in the Champions League on Wednesday, are fourth on 21 points, two behind AC Milan — who were held to a 2-2 draw at Lecce on Saturday — and eight adrift of leaders Juventus.
Second-placed Inter Milan, with 28 points, host mid-table Frosinone later on Sunday.
The reigning champions won both matches against Empoli 2-0 last campaign.
Empoli, who have lost eight of their 12 league games this term, moved out of the relegation zone to 17th on 10 points.