Manager Greg Abbott believes Danny Livesey is "desperately unlucky" to have lost his place in the Carlisle defence.
The big centre-half was replaced by Peter Murphy in the back four for the 1-0 win against Colchester on Saturday.
Abbott said the decision, which he made to gain a left and right-footed balance with his two central defenders, had upset Livesey. But the Blues boss insists he stands by his selection after Murphy partnered Lubo Michalik to help Carlisle keep a clean sheet.
"I like the balance between my central defenders," Abbott told the News & Star. "Lubo has been very good and I think he deserves his place. Last week at Sheffield United he was tackling with the outside of his right foot and coming too narrow, leaving space behind him.
"We brought Murph on for Danny at half-time and I stuck with that on Saturday.
"Danny is desperately unlucky and desperately disappointed. As a manager you have to understand that and live with it. We make tough decisions and that's the way it is."