The defender rued the loss of the Brazilian to PSG, but revealed that he hopes club CEO Adriano Galliani can sign a big-name replacement before the start of the 2012-13 season
The Brazilian completed his €42 million move to the French capital on Saturday in the second most expensive transfer for a defender in the history of football after Rio Ferdinand's switch from Leeds to Manchester United in 2002.
Antonini acknowledged the loss of Thiago Silva as a big hit to the Serie A side's ambitions for next season, but kept his faith in CEO Adriano Galliani's ability to pull off a major coup in the transfer market.
"Thiago is the strongest defender in the world, AC Milan have suffered a great loss. I'm sorry he is gone, he is a dear friend, we have been together for four years with the Rossoneri," Antonini told reporters at Milanello.
"The club has taken this decision and we have to move on. We're not worried, Galliani often makes big hits at the end of the transfer window."
Thiago Silva joined AC Milan in 2009 from Fluminense and went on to become a key player at San Siro.