AC Milan warmed up for their Champions League group opener against Anderlecht on Tuesday by suffering a shock 1-0 home defeat to Serie A strugglers Atalanta.
Milan, who lost the spine of their team earlier this summer after selling Zlatan Ibrahimovic and Thiago Silva to Paris Saint Germain, opened their season with a first home defeat to Sampdoria.
And despite a promising 3-1 win over Bologna two weeks ago, it was more of the same at the San Siro where Milan were stunned by a superb 65th-minute drive from Luca Cigarini.
Atalanta's first win of the campaign put them in positive territory after they started the season minus two points for their role in the 'Calcioscommesse' illegal betting scandal.
But Milan's second home defeat will be the big talking point Sunday ahead of the rest of the league fixtures.
With Dutchman Nigel De Jong and Massimo Ambrosini marshalling the midfield and Kevin Prince Boateng in the playmaker's role, Milan coach Massimiliano Allegri sent out a team which, on paper, looked good for the three points.
But despite dominating, the rossoneri looked disorganised and were ultimately guilty of failing to capitalise on the chances they did create.
Allegri will be under further pressure but called on his team to get wise to the need for conviction.
"We need to discover our belief, we're not consistent enough and at times everything is just becoming more difficult," he complained.
"The guys have to grow up and realise that playing in fear doesn't get us anywhere.
"Obviously it's not good to lose like this but we have to look ahead to the Champions League so we can make amends."
Boateng, playing with an arm brace following recent surgery on a broken hand bone, was a constant menace for the Atalanta defence. But when the German-born Ghanaian created space for himself, the end result was often off-target.
It was a one-sided affair in the first half but when Milan defender Luca Antonini made a desperate attempt at a clearance, Cigarini pounced on the loose ball to shave Christian Abbiati's post in the 20th minute.
Minutes later a superb strike by Milan's teenage striker Stephan El Sharaway rebounded off the diving Andrea Consigli and was bundled to safety.
Ambrosini then won the ball in midfield and broke free to shoot only to send his drive straight at the keeper.
At the other end Abbiati had to dive to parry an angled strike from Argentinian Maximilian Moralez.
Milan came even closer to breaking the deadlock before the interval but two superb shots by El Sharaway and then Boateng came to nothing.
A strike from Atalanta defender Davide Brivio brought a two-fisted save from Abbiati and at the other end Consigli did the same to parry a solid effort from El-Sharaway.
Abbiati, however, could only dive in vain when Argentinian striker German Denis laid a superb ball off for Cigarini at the edge of the area before sending his first-time strike inside the far post.
Allegri tried to make amends by giving Spain international Bojan Krkic his Milan debut and to be fair the hosts were unlucky when Pazzini twice failed to connect with probing balls close to goal.
In the end Milan were lucky to go just one goal down after Moralez missed a superb chance in the closing minutes.
Earlier Saturday, Marco Sau scored a 83rd-minute leveller for Cagliari as the Sardinians stunned fellow islanders Palermo to grab a share of the points in Sicily.