Italian champions Juventus slumped to a 3-2 defeat at Sampdoria in Serie A on Sunday while hapless Benevento were denied their first point of the season when they lost 2-1 at home to Sassuolo in stoppage time.

Two second-half headers from Mauro Icardi gave Inter Milan a 2-0 win at home to Atalanta, which took them two points above Juve into second place to stand two points behind Napoli, and left the Argentine with 13 goals from as many games.

Federico Peluso's 94th-minute winner for Sassuolo, which came minutes after his team missed a penalty, meant bottom team Benevento were condemned to a record-extending 13th straight Serie A defeat.

Juve trailed 3-0 at Sampdoria before stoppage-time goals by Gonzalo Higuain, with a penalty, and Paulo Dybala made the score more respectable.

Juventus rested goalkeeper Gianluigi Buffon and defender Andrea Barzagli, who both confirmed their international retirements after playing in Monday's 0-0 draw with Sweden which meant Italy failed to qualify for next year's World Cup.

They missed a host of first-half chances then collapsed after the break as Samp maintained their perfect home record.

Duvan Zapata headed Sampdoria ahead in the 52nd minute, Lucas Torreira blasted the second and Gian Marco Ferrari turned in Fabio Quagliarella's cross from the byline for the third.

"It was one of our best first halves of the season and we just needed to keep our cool in front of goal," said Juve coach Massimiliano Allegri. "They scored three goals from four shots."

Icardi put Inter ahead in the 52nd minute against Atalanta when he got away from his marker to head in Antonio Candreva's free kick and struck again with a superb glancing header from Danilo D’Ambrosio's cross on the hour.

Napoli, 2-1 winners over visiting AC Milan on Saturday, lead the standings with 35 points from 13 games ahead of Inter on 33, with both teams still unbeaten. They are followed by Juventus on 31, AS Roma on 30 and Lazio with 28.