Defender Chris Baird and striker Darren Bent are among those to have been released by Derby County following their play-off disappointment.
Defender Jason Shackell will also not see his contract renewed, having, like Bent, spent much of last season out on loan.
Baird, 36, played a regular role for the Rams last season having joined in 2015 from West Brom, while Bent, a former England international, scored 28 goals in 84 appearances after joining from Aston Villa but ended the last campaign on loan at Burton Albion.
Shackell, who like Bent is 34-years-old, was on loan at Millwall in the latter part of the season having played 62 times for the Rams, scoring twice.
The loan deals for Sam Winnall and Kasey Palmer, from Sheffield Wednesday and Chelsea respectively, have also ended.
Out of contract under-23 squad players who have not been offered new terms are Alex Cover, Emil Riis Jakobsen, Kyron Stabana and Matthew Taylor.