AC Milan risk missing out on European football once again after slumping to a 2-1 defeat to Atalanta.
Sassuolo could soon snatch sixth place from the ailing Rossoneri, who conceded an overhead kick to Mauricio Pinilla and a second-half goal from Alejandro Gomez at the Stadio Atleti Azzurri d'Italia.
Summer signing Luiz Adriano had given Milan an early lead, but his penalty was not enough.
After a minute's silence in memory of former Milan player and manager Cesare Maldini, who died on Sunday, the Rossoneri got under way and soon won a penalty when Guglielmo Stendardo handled.
Adriano, who had not scored in the league since November, duly fired the visitors ahead with a perfectly taken spot-kick.
Atalanta responded well and almost equalised through Gomez and then Jasmin Kurtic before Pinilla did find the leveller just before half-time, the Chilean turning home an acrobatic shot.
Milan seemed short on ideas when play resumed and Atalanta exploited their apathy to take the lead in the 62nd minute.
With the Rossoneri defence snoozing, Dutch midfielder Marten De Roon fed Gomez for an easy finish from a one-on-one.
Mario Balotelli's introduction as a late substitute saw Milan improve, however, and Marco Sportiello did well to deny the on-loan Liverpool striker in the 75th minute.
Moments later, Luca Cigarini made a desperate goal-line clearance to further frustrate Milan.
As time ticked away in Bergamo, the home players retreated en masse in order to preserve three vital points in their battle against the drop.