Duke made 59 appearances for Hull over seven years
Championship club Hull City have released four senior players, three days after ending their season with defeat at Bristol City.
Long-serving goalkeeper Matt Duke, striker Craig Fagan, defender Anthony Gardner and midfielder Tijani Belaid have all been allowed to leave.
Both Duke, 33, and Fagan, 28, played for the Tigers in the Premier League.
Former Spurs centre-half Gardner, 29, spent much of the season on loan to Crystal Palace.
Duke had spent seven years with Hull since joining from Burton Albion, and in 2008 underwent a successful operation to remove a testicular tumour.
Tunisian Belaid, 23, failed to make the necessary appearances to trigger a two-year extension on his initial deal signed when arriving on a free transfer in January.
Fagan has been injured for much of 2010/11 and made only four starts under manager Nigel Pearson.