And while Northampton were winless in their last seven games, six of those results had been draws - before Tuesday's 3-2 defeat by Burton.
"The club must always come first but that doesn't make this decision any easier," added Cardoza.
"I, my fellow directors, the staff and supporters all wanted Ian to succeed.
"I really hoped Ian would prove a successful manager here, but I did not see enough signs that we were improving as a side.
"Ian had put together a decent squad, and in a way that made our league position all the more unacceptable, and we are at a crucial time of year.
"I wanted to make this change now to give us time to go through a detailed recruitment process and to give the new man time to assess the squad before the end of the season, to look at the budget for next season and have a full summer to recruit and make the changes they see fit.
"No-one is ruled in and no-one is ruled out as we begin our search for our next manager. I think this will be an attractive job.
"We were one of very few clubs in League One or League One to spend money in January and we have some talented players under contract for next season with plenty of scope for any additions to be made in the summer.
"This appointment will be one of the biggest decisions since I have been here, we need to get things as right on the field as we are off it."
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