Steven Fletcher, Morgan Fox and Fernando Forestieri are set to leave the club at the end of the month.
All three have rejected short-term extensions to their contracts, to take them to the end of the prolonged season due to the coronavirus outbreak, and that would appear to signal their departures when their current deals run out on June 30.
Sam Hutchinson and Sam Winnall will be released when their contracts expire on June 30 and talks are ongoing with regard to possible loan extensions for Alessio Da Cruz, Jacob Murphy, Connor Wickham and Josh Windass.
David Bates will return to his parent club Hamburg at the end of June.
Meanwhile, Kieran Lee, Atdhe Nuhiu and Paul Jones have signed short-term contract extensions to the end of the current campaign.
The 2019-20 season was suspended in March due to the COVID-19 pandemic and authorisation was granted for clubs to extend the contracts of players due to expire on June 30.