Domenico Berardi's hat trick fired Sassuolo to a 3-2 victory over nine-man AC Milan on Sunday afternoon -- but it included a highly controversial ghost goal.
The Italian forward put Sassuolo in a strong position with two strikes in the first half-hour of the contest, with the first having come after Milan keeper Diego Lopez fumbled his shot before appearing to prevent it crossing the line.
Milan forward Giacomo Bonaventura reduced the arrears in the 33rd minute and then teammate Alex headed in an equaliser early in the second half.
The visitors then lost Bonaventura in the 57th minute for a double booking and Berardi put Sassuolo back in front 12 minutes from time to hand his side their 10th win of the campaign.
Milan ended the game down to nine men after substitute Suso was shown a straight red after a late foul on Sassuolo's Francesco Magnanelli.
Sassuolo, who last week ensured their Serie A status for another campaign, climbed into to 12th place and in the process ended Milan's faint hopes of qualifying for next season's Europa League.
The Rossoneri are 10th in the standings, eight points adrift of sixth-place Sampdoria with two games remaining.
Milan dominated in possession but fell behind in the 13th minute.
Lopez could not hold on to Berardi's bullet strike from 25 yards and -- with goal-line technology not available in Serie A until next season -- the officials ruled that the ball had crossed the line.
Sassuolo doubled their lead in the 31st minute when Simone Missiroli sent Berardi through on goal and the forward beat Lopez with a left-footed strike from the heart of the area.
Milan players complained that the goal should have been disallowed for a Berardi offside but their appeals fell on deaf ears.
Two minutes later and the Rossoneri replied.
A great play by Bonaventura saw the Italian striker get past two defenders and hit a right-footed shot from 15 yards past a helpless Sassuolo goalkeeper Andrea Consigli.
Milan almost pulled level before the interval but Consigli did well to save Keisuke Honda's close-range attempt.
AC Milan coach Filippo Inzaghi made his first substitution after the re-start with Suso replacing an injured Ignazio Abate.
Suso made an impact soon after when he sent in a cross which Consigli failed to clear, leaving Alex to head the ball into the back of the net in the 51st minute.
Milan were reduced to 10 men when Bonaventura was shown his second yellow card for a handball.
Sassuolo almost made Milan pay before the hour but Lopez made a full-stretch save to clear Nicola Sansone's hard drive from 25 yards.
Lopez then denied Berardi from close range.
Berardi did find his third of the afternoon shortly after.
Simone Zaza fed Berardi in the box and he hit a left-footed shot towards the centre of goal to beat Lopez and celebrate his 14th goal of the campaign.
With seconds remaining, Suso was handed his marching orders in what capped off a disappointing afternoon for his side.