Blerim Dzemaili has given Napoli a 1-0 lead over Sassuolo in their Serie A match at the Stadio Alberto Braglia.
Marek Hamsik had the first chance of the game for the visitors, but after receiving the ball in space on the edge of the box, he fired a low strike just wide of the goal.
Hamsik threatened for Napoli minutes later and again failed to trouble the keeper with a shot from distance.
Sassuolo came close to breaking the deadlock through Antonio Floro Flores, who drilled a free kick narrowly wide of the post.
The visitors wasted a big opportunity to open the scoring when Gonzalo Higuain latched onto a ball over the top from Hamsik, but could only direct his effort straight at the keeper.
They came close again moments later as Lorenzo Insigne was slipped into the box and saw his shot beaten away by Gianluca Pegolo.
Napoli continued to press and Pegolo had to be alert again to deny Higuain's fierce shot from close-range.
In the 37th minute the visitors made their dominance pay, as Dzemaili latched onto a loose ball just outside the box and fired into the bottom corner.
