"Thank you Fiorentina for the trust and for giving me the opportunity to play in the most beautiful city in Italy. I will not disappoint you," Spaniard Tello said on Twitter.
Third-placed Fiorentina play Genoa, who are 16th in Serie A, on Sunday.
(Reporting by Marianna Ciabach-Malinowska in Gdynia, editing by Ed Osmond)
