Milan's recent slump in form continued on Saturday night as Gennaro Gattuso's side were surprisingly beaten by Serie A strugglers Benevento.
The away team remain bottom of Italy's top flight despite the win, but Pietro Iemmello's confident finish and the defence's solid performance will give manager Roberto De Zerbi belief that his side can return to Serie A soon after their inevitable relegation.
Milan had an early penalty appeal waved away as Patrick Cutrone went to ground before Fabio Borini's low cross eluded Andre Silva following Christian Puggioni's save.
Ricardo Rodriguez had an embarrassing moment early on when his back pass almost ended up in his own net, but Gianluigi Donnarumma scrambled back to clear the ball off the line.
Just before the half hour mark Benevento took a shock lead, Iemmello timing his run perfectly to latch onto a Nicolas Viola pass and finish under Donnarumma.
Milan, who can finish in the Europa League qualification spots but face competition from Atalanta, Sampdoria and Fiorentina, nearly struck back through Cutrone but his effort was dragged comfortably wide.
In the second half, Benevento went close to doubling their lead as Danilo Cataldi went fired just over the crossbar.
Milan went agonisingly close to an equaliser through midfielder Franck Kessie, who has impressed in Serie A this season, but the Ivory Coast international saw his long range shot come crashing off the woodwork after a good run.
Gennaro Gattuso's side have hit something of a rut in recent weeks after the resurgence under the former Italy international and are currently winless since beating Chievo 3-2 back in March.
Frustration around San Siro grew even further when the impressive Puggioni saved from Cutrone's header and neither Giacomo Bonaventura or substitute Nikola Kalinic could finish on the rebound.
Milan's search for a goal was given a major boost when Cheick Diabate was sent off for a second yellow card after a rogue elbow caught Rossoneri defender Leonardo Bonucci in the face.
However, they ultimately drew a blank and could drop down to seventh on Sunday, should Atalanta beat Torino.