Mario Gaspar has been released by Watford.
The midfielder is the son of Arsenal technical director Edu.
Gaspar came through the system at Arsenal before moving to Watford, but has now been allowed to come off contract.
Also departing the Championship club are Domingos Quina, who has moved to Udinese permanently, Jurgen Elitim has joined Legia Warsaw and Ober Almanza joins Orsomarso SC on loan until the end of the year.