The Brazil international looked set to sign for the Ligue 1 leaders but performed a dramatic U-turn on Thursday, declaring that he wished to remain at San Siro
The 22-year-old seemed bound for the Parc des Princes after the Ligue 1 leaders agreed a fee with the Rossoneri for the player.
However, the move seemingly broke down on Thursday afternoon when Pato declared his intention to remain at San Siro, a development which resulted in Milan abandoning their pursuit of Manchester City forward Carlos Tevez.
It was thought that the Pato deal could yet be resurrected but Ancelotti conceded defeat during a press conference on Friday.
"It's over. He hasn't arrived because we were waiting for an agreement between AC Milan and Manchester City for Tevez.
“It's the player's decision then. We wanted to bring in a player to improve the team. We have time until the end of the window [to find someone else].”
According to reports, Ancelotti, who worked with Pato during his time in charge of Milan, has now turned his attention to signing another Brazilian, Internacional's Leandro Damiao.