Ten-man Sassuolo dealt AC Milan a heavy blow in their bid to qualify for Europe by defeating the Rossoneri 2-0 on Sunday.
The Neroverde started the day six points behind sixth-placed Milan but will now look to overtake them after goals from Alfred Duncan and Nicola Sansone secured an impressive victory for the Mapei Stadium side.
Eusebio Di Francesco's men even managed to dominate the final exchanges despite losing Gregoire Defrel to a late red card.
With time running out in Milan's mission to secure Europa League football, they started rather enthusiastically in Reggio Emilia, with Japanese playmaker Keisuke Honda twice going close inside 10 minutes.
Francesco Acerbi denied Carlos Bacca before Sassuolo goalkeeper Andrea Consigli pounced on Giacomo Bonaventura's swerving free-kick.
The hosts took the lead against the run of play in the 27th minute. A well-worked corner-kick routine saw Domenico Berardi pass the ball to Sansone, who set up Duncan for a powerful finish.
Sassuolo should have doubled their lead before half-time but neither Sansone nor Berardi could put gilt-edged chances away.
Berardi got teenage keeper Gianluigi Donnarumma working again as soon as play resumed and the home pressure showed no signs of abating as the second half wore on.
Indeed, in the 72nd minute, Sansone made it 2-0 when sweeping Sime Vrsaljko's through-ball beyond Donnarumma with an angled drive.
Sassuolo's hopes of holding on appeared to suffer a setback when striker Defrel picked up a second yellow card, but lacklustre Milan could not find a way through.