But Franck Kessie's 20-yard drive got Milan up and running at the MAPEI Stadium on Sunday, with Suso and Samu Castillejo also scoring from outside the penalty area in the second half.
A second from Suso in injury time sealed a win that breaks a run of three straight draws in the league and moves the Rossoneri into the top half, while Sassuolo – who got a goal back through Filip Djuricic – stay fifth after missing the chance to climb into second spot.
Suso thundered an early strike against the crossbar from a tight angle but Kessie should have given Milan the lead in the 26th minute - his dinked finish beat Andrea Consigli but lacked enough power to cross the line, allowing Pol Lirola to clear off the line.
Federico Di Francesco missed a similarly golden chance when he drilled at the legs of Gianluigi Donnarumma when fed by Domenico Berardi, then Ignazio Abate's wonderful challenge prevented a certain Sassuolo goal.
Kessie made amends for his earlier miss by breaking the deadlock in the 39th minute, smashing a low drive into the bottom-right corner from 20 yards to round off a 50-yard run.
Another fine finish doubled Milan's advantage five minutes after the restart, with Suso – making his 100th Serie A appearance – cutting in off the right flank to whip home a 25-yard curler.
Milan gave up leads in their least two Serie A games but Castillejo seemingly made the points safe, scoring his first Rossoneri goal with another terrific left-foot shot from distance on the hour mark.
Although Sassuolo responded through Djuricic to spark a nervy finale, Suso scored again with the last kick of the game – his deflected shot surviving a VAR review – to boost Gattuso.
What it means: Relief for Gattuso
Gattuso has been batting away questions about Conte all season but speculation reached fever-pitch in the build-up to this game. In truth, Milan did not play that well – although they were missing injured striker Gonzalo Higuain – but individual quality hauled them to a much-needed victory in front of the watching sporting director Leonardo.
Abate tackle a decisive moment
Kessie, Suso and Castillejo, deployed as a centre-forward, will make the headlines for their wonderful goals but Abate deserves his share of the credit for a tremendous challenge when the scores were level. Di Francesco was poised to tap in a Kevin-Prince Boateng cross when Abate arrived, seemingly out of nowhere, to make a vital intervention.
Wasteful Di Francesco costs hosts
There was little Di Francesco could do about Abate's brilliant defensive instincts but the Sassuolo attacker had already wasted an excellent opportunity to score the first goal of the game. The 24-year-old has only scored once in the league this season and his lack of composure told. Had Di Francesco found the net, Milan could have crumbled.
Key Opta facts
- AC Milan have scored the most goals from outside the box (five) in the current Serie A (all their last five goals in the competition).
- This was the first time Milan scored four goals from outside the box in the same Serie A match since Opta started collecting this data (2004-05).
- Franck Kessie has scored five of his seven Serie A goals for Milan in games away from home.
- Suso has been directly involved in the most goals (five, thanks to two goals and three assists) for Milan in Serie A this season.
- Filip Djuricic scored his first Serie A goal against the Rossoneri (38 games played, 26 shots taken).
- Sassuolo have conceded eight goals in their last three Serie home games.