AC Milan coach Leonardo offered no excuses after their 2-0 defeat to Palermo.
Second-half goals from Fabrizio Miccoli and Mark Bresciano earned the Sicilians a famous victory.
Leonardo said: "What happened? First of all we must give credit to Palermo, who were very organised tactically and physically strong.
"They play in a similar style to ours, with many players on the attack, today they just did it better.
"It was an extremely open game and those two goals at the start of the second half decided the result."