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A first goal in Milan colours for Luka Jovic got the scoreboard ticking over, but it was a long wait for the fans at San Siro, coming in the 43rd minute of a largely uneventful first half.

Christian Pulisic added a second with a touch of class, controlling a long ball beautifully before lobbing it expertly into the back of the net just five minutes into the second period.

Fikayo Tomori scored the third from a corner routine to seal the deal, but there was still time for Milan to again show its defensive frailties when a free-kick from Marco Brescianini was allowed to go all the way through and past Mike Maignan for a Frosinone consoloation.

Milan remains in third spot on the table, three points back from Inter Milan, which will be hoping to climb back into top spot above Juventus with a win against defending champion Napoli on Monday.

Just one win in five Serie A matches had seen Milan drop off the title pace and Pioli’s side knew there was no room for error after Juve's last-gasp win at Monza.

Milan was without the likes of Malick Thiaw, Rafael Leao and Olivier Giroud, and full-back Theo Hernandez lined up in the middle of a badly depleted home defence.

A largely uninspiring first half was lit up by Jovic lashing home a superb left-footed volley two minutes before the break.

It was the Serbia striker’s first goal in 10 appearances since joining Milan from Fiorentina in September.

Frosinone, beaten 2-0 at San Siro by Inter Milan last month, started brightly but Milan had the first opportunity when Yunus Musah’s centre took a wicked deflection and Stefano Turati had to react sharply at his near post.

Milan slowly built up a head of steam and Alessandro Florenzi fired wide, while Samuel Chukwueze’s powerful drive was deflected to safety.

Frosinone full-back Anthony Oyono broke forward but his 25-yard effort went wide as his wait for a first senior goal continued.

The visitors should have taken the lead three minutes before the break after Marvin Cuni dispossessed Tomori.

Cuni had a clear run on goal but the Albania striker lacked conviction and Milan goalkeeper Mike Maignan stood tall to save.

Frosinone were punished for their profligacy within 60 seconds as Simone Romagnoli’s poor pass was picked off by Pulisic, who spotted the unmarked Ruben Loftus-Cheek to his right.

Loftus-Cheek found Chukwueze quickly and, although Romagnoli got his head on the cross, Jovic was waiting to volley in from eight yards.

Milan doubled its lead five minutes after the interval in route-one style.

Maignan’s long punt was brilliantly brought down by Pulisic, who cut across three defenders to present himself with a shooting opportunity.

Turati rushed out to narrow the angle but the American showed great composure to lift the ball over him for his fifth goal of the season.

Tomori added a third after 74 minutes from a well-worked corner routine, the England defender latching on to Jovic’s far-post header to force home his second goal of the season from close range.

Frosinone gained some reward for its determination to keep going eight minutes from time.

Brescianini’s wide free-kick escaped everyone in a crowded penalty area and surprised Maignan, who had no chance of preserving his clean sheet.