A Rovers statement read: "The club is extremely disappointed by John Eustace's request to hold discussions with another club at such a crucial stage of the season, but this has now been reluctantly granted.
Eustace - who joined Blackburn a year ago - admitted on Sunday after the FA Cup defeat to Wolves : "I’ve come to the club to help rebuild it and help us push up the league and I’ve been very happy here.
With the squad bolstered, key players returning from injury and Rovers currently in a strong position in the Championship, the club and players remain focused on achieving the best possible outcome this season.".
Derby, who head into Tuesday's clash with Oxford inside the bottom three, sacked Paul Warne last week and have made former midfielder Eustace their top target.
"With significant investment being made during the January transfer window...the board and ownership feel the club are in good position to challenge for one of the play-off places this season.
