Paulo Fonseca was left disappointed with Milan's lack of defensive responsibility in their shock 2-1 defeat to newly promoted Parma on Saturday. 

Milan were stunned inside 83 seconds when Dennis Man gave the hosts a shock lead, only for Christian Pulisic to restore parity just after the hour-mark. 

However, substitute Matteo Cancellieri struck in the closing exchanges to secure their first triumph over Milan in Serie A since 4-2 win back in March 2014. 

It marked an early bump in Fonseca's tenure with the Rossoneri, acknowledging that his side must improve at the back to succeed this season. 

"I'm disappointed. It's difficult to explain our defensive attitude. It's clear that we have a defensive problem," Fonseca told a press conference.

"For Parma it was too easy when they attacked. I'm not just talking to the defenders, I'm talking about the whole team, how they defend collectively and individually.

"I take responsibility for what the team does, but we have to recognise these defensive problems."

Milan created the better chances during the contest at Stadio Ennio Tardini, but only five of their 17 shots were on target, the same number as Parma managed from eight fewer attempts. 

The visitors also underperformed their expected goals (xG) by 1.01, missing three big chances while also striking the woodwork in the encounter. 

Of the 90 duels between the two sides, Parma had a success rate of 54.4% compared to Milan's 45.6%, with Fonseca left bemused by his sides underwhelming display.

"The team works well during the week, I think I see improvement in view of the match. Then today we arrive here and in the first situation we concede a goal," Fonseca added.

"We behaved badly defensively in all moments of the match. (There's) a problem to solve, of attitude. We need to work as a team.

"We lose the ball too easily. This allows a team that defends deep to create chances. We have made mistakes in preventive marking, defensive recoveries that we do not do together."

Promoted Parma pulled off a shock 2-1 home victory over AC Milan in Serie A on Saturday.

Defeat for Milan, their first against Parma in the top-flight since 2014, extended Paulo Fonseca's wait for his first win as coach of the Rossoneri.

Parma stunned Milan with an early opener through Dennis Man, who struck with his first touch after 84 seconds, having also netted on the opening weekend of the season.

Man is the first Parma player to score in the first two matchdays of a Serie A season since Alberto Paloschi in 2009-10.

Christian Pulisic equalised for Milan in the 66th minute after Rafael Leao fed a low pass into the path of the American winger, who finished from close range.

But, after being set up by fellow substitute Pontus Almqvist, it was Matteo Cancellieri who restored Parma's lead with 13 minutes left, and Parma held on to seal a famous victory.

Milan, who scored two last-gasp goals to secure a 2-2 draw in their season opener against Torino, remain on one point in the standings ahead of a key trip to play Lazio next week.

Data Debrief: Milan pay price for poor finishing

With Alvaro Morata out through injury, Milan lacked a cutting edge in this contest.

They managed 17 shots, but found the target with just five of them, scoring just once from an expected goals (xG) total of 2.01. Leao was among the main culprits, failing to trouble the goalkeeper from four attempts.

Parma managed the same amount of attempts on target as Milan (five) from just nine total shots, and Cancellieri has developed a reputation as a super sub.

Five of his six goals in Serie A have come as a substitute and four of those have come from the 70th minute of play onwards.