Mastantuono left River Plate at the end of last season to join Real Madrid.
Bottinelli thinks that working with Real's coach, Xabi Alonso, will be beneficial for Mastantuono.
"I'm happy to see Franco doing well at his new club," Bottinelli said.
"As a young player, he needs time to adjust, but I think Xabi's guidance will help him reach his full potential quickly."
Bottinelli also acknowledged that comparisons to Leo Messi are inevitable, but he advises against putting too much pressure on Mastantuono.
"We know Leo Messi is a football legend, and hopefully, Franco can follow in his footsteps," Bottinelli said.
"However, we shouldn't put too much pressure on him. He needs time to develop and grow as a player."