Derby County's chief executive Tom Glick has revealed that the club have rejected four bids for defender Jason Shackell.
County manager Nigel Clough conceded last week that Shackell would be allowed to leave Pride Park if an acceptable offer were received.
However, Glick has described the 28-year-old as "an essential player" for the Rams.
"We've turned down four bids from three different clubs on Jason at this point," said Glick. "Simply put, Jason is an essential player for us.
"He played every minute of every game 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."
Shackell joined Derby last summer from Barnsley.
