"For me, it 's the chance of a lifetime. I know what my job will be. For me, it's an honour," Castillo explained.
"When Fiorentina called me there and then I didn't believe it was true."
The Viola's director of sport Pantaleo Corvino explained the club's decision to gamble on a veteran who has played most of his career in Italy's lower leagues.
"Josè will take the No 9 shirt, that of the bomber. We could have chosen other more famous names but this year we want players who are motivated and Castillo is one of them," Corvino said.
"He will not mess up. He will be an alternative to Alberto Gilardino. Like me, he has gone through all the divisions before ending up in the big league.
"To me and Prandelli he seems like the right choice."