The visitors defended well throughout the game and managed to take a point in a 1-1 draw, and although Napoli were the favourites, Hamsik said that they could not be expected to win every game.
"There are no easy games in this league," Hamsik told reporters. "After losing 7-0 at the weekend, Sassuolo tried three times harder against us.
"Everyone thought these would be three easy points, but we knew that would not be the case. We could have done more. We didn't press as we should have. We started well, but we became disjointed after the goal. We lacked a spark.
"Sassuolo defended well, they changed shape, but we are the only ones to blame."
The point was Sassuolo's first of the season.