The Welshman, who has played in a vareity of positions for the Spireites, is close to completing a move to League One Portsmouth in a deal that will net Chesterfield in the region of £70k.
His exit may come as a surprise to supporters, but Caldwell has long known it was a possibility.
“I don’t think it’s a blow, it something we were prepared for all summer,” he said today.
“The player intimated at the end of last season he wanted to leave.
“It’s taken longer than others who said that.
“We were always prepared, we signed Jerome in preparation for that.
“It’s obviously disappointing Jerome got injured but we were always ready to act and we now have scope for future development of the squad as well.”
Caldwell says the incoming finance from Donohue’s move allows him to go and get other players now, whereas before the sale things were very tight.
“I think it’s a good thing for the club,” he said.
“It gives us an opportunity to strengthen the squad.
“Our aim was to come out of the window a stronger squad, ready to be successful this season and Dion’s sale gives us that opportunity.”
Donohue earned a contract at the Proact after a successful trial in the summer of 2015.
He has made 65 appearances as a Spireite, many of them on the left hand side of defence.
But he sees himself as a midfielder and has played a few times in the middle of the park, as well as on the left and even as part of a central defence of three.
Caldwell has already added Jordan Flores on loan from Wigan, a midfielder who can play on the left and may well take Donohue’s place in the side tomorrow when Port Vale visit.