Aberdeen are planning a fresh move for Dunfermline captain Scott Wilson as they bid to shore up their leaky defence.
The experienced former Rangers stopper is perceived to be the perfect partner for Zander Diamond, as Calderwood aims to beef up his defence following a number of key departures.
"Clearly our defensive frailties are a major cause for concern. Our goal difference is minus 13 and, for a team of this standing, that's ridiculous.
"A lot has been made about the fact we lost Russell Anderson but we can't blame all our problems on his departure. Michael Hart, Markus Heikkinen and Kevin McNaughton have all left," said Calderwood.