Watford defender Joel Ekstrand will leave at the end of his contract after four years at Vicarage Road.
The 27-year-old, capped twice by Sweden, has not appeared for the Hornets since suffering a cruciate knee ligament injury in March last year.
Meanwhile, Watford have extended the contract of 19-year-old striker Alex Jakubiak for a further year.
But Under-21 players George Byers, Josh Doherty, Matt Hall, Uche Ikpeazu, Jorell Johnson, Mahlondo Martin, Bernard Mensah, Luke Simpson and Alfie Young have all been released.