The 27-year-old centre-half, who passed a fitness test on his ankle ahead of the Millers' clash with Cheltenham, limped out of the 4-2 victory in the first half and X-rays have shown a cracked bone in his fibula which will keep him out for up to five weeks.
"I could have cried when it was confirmed Craig will be out for four or five weeks," Evans said. "A number of hours in the hospital including several X-rays confirmed he has broken a small bone at the bottom of his fibula.
"He has been brilliant for us and is a loss but added to the big players we have missing, it really is another big blow, but we will deal with it.
"I will speak to the chairman and I can say now I do have a few options to consider and it is not straightforward, it needs to be considered carefully."