Sassuolo's perfect start to the campaign ended on Sunday with a 2-2 draw at home to Atalanta.
Atalanta goalkeeper Marco Sportiello saved Nicola Sansone's spot-kick in the sixth minute.
Mauricio Pinilla put Atalanta ahead on 13 minutes with an overhead kick to beat Sassuolo goalkeeper Andrea Consigli.
Francesco Magnanelli equalised in the 22nd minute with a 30-yard drive but 11 minutes later, Pinilla struck past Consigli to put Atalanta back in front.
Seven minutes later, Sassuolo equalised through Antonio Floro Flores's 25-yard volley.
Shortly after the re-start Pinilla was handed his marching orders after earning his second yellow card for a foul on Federico Peluso.
Sassuolo's Sime Vrsaljko was sent off with six minutes remaining for a second yellow card after bringing down Maxi Moralez in the area.
Moralez saw his resulting penalty saved by Consigli.
ends