AC Milan moved into the top half of the Serie A table with just their second league win of the season at Sassuolo.
Franck Kessie drilled home after having a shot cleared off the line, Suso curled in a second and Samu Castillejo added a third from long range.
Spaniard Suso added a deflected fourth in injury time, which was awarded by the video assistant referee (VAR).
Sassuolo missed the chance to go second with ex-Southampton loanee Filip Djuricic stroking in a consolation.
Parma continued their impressive start to the season on their return to the top flight as ex-Arsenal forward Gervinho scored the winning goal to beat Empoli 1-0.
Former West Ham striker Simone Zaza scored a late winner as Torino won 1-0 at Chievo and ex-Aston Villa midfielder Jordan Veretout netted a penalty as Fiorentina defeated Atalanta 2-0.
Bologna beat Udinese 2-1, while Genoa won at Frosinone by the same scoreline.