The 27-year-old had many offers on the table during the summer but elected to choose the Serie A outfit because of the freedom they allow him to play with
The Spaniard has appeared in all of Vincenzo Montella's side's games this season so far, helping the Florence outfit to sixth in the league, but is yet to score his first goal for his new club.
"During the summer I received many offers, some very interesting ones, but in the end I preferred Fiorentina," Borja told Marca.
"That's because, as well as the financial aspect of the deal, I was joining a club who would allow me to express myself.
"I feel happy in Florence and the team is ideal for my characteristics - and I think I can still improve as a player."
The 27-year-old also spoke of his respect for his new boss, who he believes is perfect to bring Fiorentina success in Serie A.
He added: "Serie A is a league where physicality and tactics command, but we can count on a great tactician like Vincenzo Montella."