Derby have rejected four bids to date for defender Jason Shackell, according to chief executive Tom Glick.
Rams boss Nigel Clough revealed earlier this month he was willing to listen to offers for the centre-back should a significant bid come in which would help fund his overall summer transfer plans and strengthen his squad.
But that is yet to materialise and Derby will not part with Shackell on the cheap, suggesting he could remain at Pride Park next season.
Glick told skysports.com: "We've turned down four bids from three different clubs on Jason at this point.
"Simply put, Jason is an essential player for us. He played every minute of every game (last season) and it's no surprise we've had interest in him, from more than those three clubs, too.
"He's a top player in the Championship and a leader for us, so it would take a lot to pry him away from Derby."