Milan's 100 per cent record was ended at the Stadio Picchi, where Livorno held out for a 0-0 draw and rattled the crossbar with Stefano Morrone. It's their first Serie A draw since March 12.
The Rossoneri have already wiped out their eight-point Calciopoli penalty and were hoping to maintain their perfect record, but Livorno are strong on home turf and eager to cause an upset.
Captain Paolo Maldini limped off after just four minutes of play to make way for Kakha Kaladze, raising further doubts over his fitness levels after a long-term injury last term.
Pippo Inzaghi set up a promising opportunity for Ricardo Oliveira that was charged down by Marco Amelia, then Clarence Seedorf drilled over the bar.
Kaka's splendid curling strike was inches wide of the top corner with Amelia beaten, then Inzaghi scuffed over from a Daniele Bonera assist. Dario Passoni gave the ball away in midfield and Kaka's ambitious lob was off target.
Massimo Ambrosini was furious when he fell inside the area on a David Balleri challenge, but the referee waved play on.
Livorno also had a scoring opportunity just before the break, as Bonera's error sparked a counter-attack that Cristiano Lucarelli fired over from seven yards.
Amelia pushed a Kaka set-piece off Inzaghi's head and there were penalty appeals for a Bonera challenge on Lucarelli. However, while Milan lost Maldini, Livorno also saw their most representative player limp off with a thigh problem, making way for Bakayoko.
Yet it was after his substitution that Livorno really began to threaten. Alessandro Nesta cleared a Balleri cross to the edge of the box, where Stefano Morrone's missile cannoned off the bar.
Giuseppe Favalli also went off with a muscular injury, letting Marek Jankulovski on to the field. Carlo Ancelotti's only unforced substitution saw Andrea Pirlo replace Gennaro Gattuso.
Dida did well to hold a Luca Vigiani glancing header and a long-range Balleri snapshot flashed across the face of goal. At the other end, Inzaghi nearly pounced on a Rahman Rezaei error, closed down by Amelia.
Kaka chested down and drilled his half-volley wide from the edge of the box, then another of the Brazilian's strikes was controlled by the Livorno goalkeeper.
In the final minute, Pirlo's long ball sent Ricardo Oliveira running, but Amelia timed his intervention perfectly to pluck it off the striker's feet and prevent a goal or penalty.
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