Zarate has since spent time rebuilding his fitness with the Under-23s side, but Silva has taken the decision to send the Argentine to Al Nasr until next summer, with the option of a recall in January.
A club statement read: "Watford FC can confirm that forward Mauro Zarate has joined UAE Arabian Gulf League side Al Nasr on loan for the remainder of the 2017-18 season.
"The Hornets hold the option of recalling the Argentine in January. The move is in line with today's (Monday, October 2) United Arab Emirates transfer deadline.
Former Fiorentina ace Zarate has made just three senior appearances for the Hornets since joining for £2.3m in January.