Sassuolo climbed above Inter Milan in the Serie A standings with a 3-1 win over Roberto Mancini's men on Sunday.
Simone Zaza and Nicola Sansone established a two-goal lead in a one-sided first half and although Mauri Icardi pulled a goal back in an improved second-half performance from Inter, a Domenico Berardi penalty sealed Sassuolo's victory.
Both teams ended the game with 10 men with Sansone and Isaac Donkor sent off, but the greater damage for Inter was their second straight Serie A defeat.
Inter coach Mancini left Icardi out of his starting XI, fielding Lukas Podolski in a more advanced position with Rodigo Palacio.
They did not get to see much of the ball, though, as Sassuolo instead dictated affairs in Reggio Emilia with Zaza twice testing Samir Handanovic in the same top left-hand corner.
That was where the ball was to nestle in the 17th minute with a case of third time lucky for the Sassuolo and Italy striker.
He received the ball from the left, teed it up just inside the area and, on the turn, flashed his shot past Handanovic with plenty of power.
The trend of Sassuolo attacking and Inter defending continued with the second goal arriving on the half hour mark, in that very same corner where Handanovic was having the most problems.
Sansone it was this time with another stunning effort from outside the penalty area which the Inter custodian got his hand to, but he could only touch it onto the underside of the crossbar, helping it on its way into the back of his goal.
Sansone nearly got in again just before half-time, but Handanovic dived at his feet to thwart him.
Inter had to do something in the second half, and something certainly changed. Icardi came on for Podolski and he soon started receiving more service than the World Cup winner had.
Xherdan Shaqiri went close, striking the right-hand post with his shot from 20 yards, before Marcelo Brozovic made his debut, almost teeing up Dodo with a deep cross which the Inter full-back headed towards the bottom corner, just where Andrea Consigli was waiting.
The Sassuolo goalkeeper was not ready for a pass back from Francesco Magnanelli which Icardi intercepted in the 83rd minute to nudge past Consigli and slot into the unguarded goal, giving the Nerazzurri some late hope.
Those were fuelled further when Sansone was given his marching orders for a clash with Fredy Guarin, a red card which, combined with yellow cards for Zaza and Berardi, deprives Sassuolo of their three first-choice strikers for their next trip to Sampdoria.
He was followed for an early shower by Donkor after he picked up a second yellow card for a foul on Zaza inside the area, which resulted in a penalty for the hosts.
Berardi sent Handanovic the wrong way to lift Sassuolo above Inter in the Serie A standards as the Nerazzurri's crisis continues.