Watford have 15 professional players registered for next season after releasing seven players, including Mark Yeates and Stephen McGinn.
Prince Buaben, Piero Mingoia, Jack Bonham, Aaron Tumwa and Stephan Hamilton-Forbes have also left.
Manuel Almunia, Jonathan Bond, Fitz Hall, Lloyd Doyley and John Eustace are also out of contract but are likely to be offered new deals.
Thirteen players have reached the end of loan deals at Vicarage Road.
A total of 21 players are poised to leave Vicarage Road this summer, although many of them are loan signings from Udinese and Granada, clubs who also belong to Watford's Italian owners the Pozzo family, and
Despite being under a transfer embargo the Hornets will be allowed to make signings on a case-by-case basis.
The beaten Championship play-off finalists will be unable to make the number of foreign loan signings they arranged last season - they finished the campaign with 11 - as
Match-day squads next season will be restricted to five loanees, with four from any one club.