Parma swoop for Castellini
The 29-year-old former Perugia and Sampdoria stopper will put pen-to-paper on a three-year deal at the Ennio Tardini stadium, though no fee for the transfer has been disclosed.
Bologna coach Francesco Guidolin expressed his disappointment at losing a key member of his squad so close to the beginning of the new Serie A campaign, but wished Castellini well.
"I'm disappointed. Just a few days before the beginning of the season an important piece of our defence has left when we already had problems in that line," said the Bologna chief.
"However, in addition to being a big-level player, Castellini is also a great person.
"We'll miss him. We give him our best wishes for this new experience in such an important and ambitious team."
However, Bologna have moved to fill the gap left by Castellini by taking Parma's defender Emiliano Moretti on a one-year loan deal.
Moretti insisted though that his move was not directly precipitated by Castellini's departure in the opposite direction, and stated that Bologna had always planned to move for him.
"Castellini's departure was not bounded to my arrival here, the club (Bologna) had the intention to sign me," said the 23-year-old stopper who spent part of last season on loan at Juventus.
"Replacing Castellini is an important responsibility, but I can guarantee a big effort.
"My aim is to become an important player for this team, an aim I can only earn through my effort and performances."