Napoli fullback Mario Rui struck two minutes from time to give his side a dramatic, rain-soaked 2-1 win at SPAL on Sunday.
Napoli, already sure of a second-place finish behind champions Juventus, went ahead four minutes after the restart when Brazilian midfielder Allan curled the ball in after his first shot had been charged down.
Sergio Floccari thought he had equalised for SPAL only to see the goal chalked off for offside following a VAR review, but they finally levelled with an Andrea Petagna penalty six minutes from time.
But Rui played a one-two with Jose Callejon before scoring with a rasping shot in the 88th minute.
Napoli have 76 points from 36 games, 13 behind Juventus, while SPAL are a comfortable 11th with 42.