Midfielder Domingos Quina has left Watford to join Italian Serie A side Udinese, with the terms of the transfer undisclosed.
He had two loan spells away from Vicarage Road last season, spending time with Elche and Rotherham United.
Meanwhile, Mario Gaspar's contract has been terminated by mutual consent.
The 32-year-old Spanish defender played 33 games in all competitions after joining the Hornets from Villarreal last July.
Midfielder Juergen Elitim, who did not make an appearance for Watford, has joined Polish side Legia Warsaw, while fellow Colombian Ober Almanza, 20, has moved back to his homeland to join Orsomarso SC on loan until the end of December.