Alessio Cerci provided an assist and hit the woodwork, but Nigel de Jong snatched Milan’s late Coppa Italia win over Sassuolo.
The victors go on to face Lazio or Torino in the quarter-finals next month.
The Round of 16 tie took place at San Siro with only 8,393 spectators and was a replay of a Serie A encounter just a week ago, when Sassuolo emerged 2-1 winners.
Cerci was given his first start in a Rossoneri jersey and had their best early chance, holding off two defenders to force a save out of Alberto Pomini at the near post.
Alessio Cerci provided an assist and hit the woodwork, but Nigel de Jong snatched Milan’s late Coppa Italia win over Sassuolo.
The victors go on to face Lazio or Torino in the quarter-finals next month.
The Round of 16 tie took place at San Siro with only 8,393 spectators and was a replay of a Serie A encounter just a week ago, when Sassuolo emerged 2-1 winners.
Cerci was given his first start in a Rossoneri jersey and had their best early chance, holding off two defenders to force a save out of Alberto Pomini at the near post.
Nicola Sansone, Leonardo Pavoletti, Giampaolo Pazzini and Stephan El Shaarawy all went close before Pazzini got in front of his marker to volley in a Cerci cross from the right. It was Pazzo’s first goal since April 2014.
Moments later Cerci nearly doubled their lead, but he turned a Mattia De Sciglio assist on to the inside of the upright.
Sassuolo had the ball in the back of the net in first half stoppages with Sime Vrsaljko nodding in a free kick, but only after he had been flagged offside. However, replays suggest it was an extremely tight decision.
Pazzini came so close to a second after the break, denied only by two great Pomini saves from point-blank range, while Sansone and Pavoletti had chances.
The referee awarded a soft penalty to Sassuolo when Cristian Zapata went shoulder to shoulder with Pavoletti and appeared to slip. Sansone converted the spot-kick to draw the Neroverdi level.
A long-range Cerci free kick was fingertipped out from under the bar, but Christian Abbiati denied Sansone and Sergio Floccari.
With four minutes left before extra time, Milan restored their advantage. Andrea Poli volleyed on to the crossbar from a splendid Daniele Bonera pass, but Nigel de Jong was ready for the follow-up. This was the Rossoneri’s first competitive victory of 2015.
Milan 2-1 Sassuolo
Scorers: Pazzini 38 (M), Sansone pen 64 (S), De Jong 86 (M)
Milan: Abbiati; Abate, Alex, Zapata, De Sciglio (Bonera 46); Poli, De Jong, Bonaventura; Cerci (Montolivo 82), Pazzini, El Shaarawy
Sassuolo: Pomini; Vrsaljko, Cannavaro, Antei, Longhi; Chibsah (Floro Flores 87), Missiroli, Biondini; Floccari, Pavoletti (Zaza 85), Sansone (Berardi 87)
Ref: Tommasi