Juventus secured the first leg of a likely domestic double as a second-half blitz, aided by two Gianluigi Donnarumma howlers, saw the holders ease to a 4-0 victory over AC Milan in the Coppa Italia final.

Medhi Benatia was the unlikely hero for Massimiliano Allegri's side, the defender scoring twice from corners to help Juventus secure the trophy for a fourth successive season.

They could add the Serie A title on Sunday if they better Napoli's result, though their superior goal difference means it is only a matter of when, rather than if, they claim the Scudetto for a seventh straight year.

Douglas Costa's long-range strike was sandwiched between Benatia's brace, while Milan's misery was complete when substitute Nikola Kalinic headed into his own net.

Gennaro Gattuso's team played well in the first half but fell apart after the break, their hopes of winning the competition for the first time since 2003 left in ruins in Rome. 

Their cause was not helped by two glaring errors from highly rated goalkeeper Donnarumma, as Milan conceded four in the space of 20 astonishing minutes.

Andrea Pirlo's presence on the field prior to kick-off drew a rousing reception from all sides of the ground, with the former Italy international – a legendary figure with both clubs – parading the trophy up for grabs in customary cool fashion.

Allegri opted to leave the out-of-sorts Gonzalo Higuain - who had managed just one goal in his last nine outings in all competitions - on the bench, instead choosing Mario Mandzukic as the focal point in attack.

The Croatian sent a downward header straight at Donnarumma during a first half that saw Juventus control possession without carrying too much of an attacking threat.

Instead it was Gianluigi Buffon who was the busier goalkeeper before the break, the veteran turning away firm shots from Patrick Cutrone and Suso as Milan did pose problems on their rare forays into opposing territory.

However, having stood toe-to-toe with their opponents for 45 minutes, Gattuso's young side collapsed in spectacular fashion after the interval.

There was little Donnarumma could do about Benatia's header to break the deadlock, the defender steering a looping header into the net from Miralem Pjanic's set-piece delivery.

However, the teenage keeper was at fault for the next two goals, starting with his failure to keep out Costa's low, left-footed drive immediately after pulling off a spectacular save to deny Paulo Dybala.

Benatia also benefited from an error to score again against a shell-shocked Milan, Donnarumma's dodgy handling dropping the ball straight into the centre-back's path, leaving him with an easy tap-in.

Blaise Matuidi was fortunate not to score an own goal, slicing a cross against the woodwork, but luck deserted Kalinic at the other end, his header glancing past Donnarumma to round out a thoroughly miserable evening for Milan.