Napoli are also set to make an official bid for the player in the coming days.
The deal will be complicated, however, after Gremio president issued a statement declaring the club’s intention to keep hold of Walace for another season.
Fiorentina are still hopeful of signing Walace after missing out of Sergej Milinkovic-Savic who moved to Lazio earlier this week.
Walace has made 30 appearances for Gremio since joining the club in 2013.