Milan lost 3-0 with Ibrahimovic substituted in the second-half.
"It wasn't an easy game for Inter, we suffered for 10 or 15 minutes, but it's impossible to win a derby without suffering. I didn't expect Inter to be so much superior," said Berti.
“Talking about that, why did Ibra leave the pitch early? Was it to do a rehearsal for Sanremo?"
Berti was referring to Ibrahimoic's plans to attend the Sanremo festival next month.