Derby are willing to listen to offers for James Bailey, Miles Addison, Lee Croft and Chris Maguire.
Striker Maguire still has two years remaining on his contract after joining the club from Aberdeen last summer, while midfielders Bailey and Croft and centre-half Addison are all entering the final 12 months of their deals.
Maguire, Croft and Addison have spent time out on loan recently, while Bailey has been overtaken in the pecking order by the emergence of Jeff Hendrick in central midfield. Addison is wanted by npower League One side Bournemouth, where he ended the season on loan.
"James, Lee and Miles have a year left on their deals so it makes good sense from that point of view to get a fee in if we can for them," said manager Nigel Clough.
"Chris, Lee and Miles barely featured for us this season and moving forwards are unlikely to, while in James' case he hasn't done anything wrong it is just that he is going to find it very hard to break up the (Craig) Bryson-Hendrick midfield pairing we have."
Steve Davies is also available for transfer after the striker, Derby's joint-top scorer this season with 12 goals, turned down the offer of a new contract on Tuesday due to "family circumstances".