The centre-back has yet to play for the Latics this season after hip surgery in the summer.
However, he made his first appearance of the season in Scotland's Euro 2012 qualifier against the Czech Republic on Friday.
Despite joining up on the understanding he played only one game there is a chance Caldwell could be involved against Spain tonight but Martinez has urged caution.
"Caldwell has been feeling good. We know he's been out for a while, but nobody knows his body better than the player himself," the Spaniard told the Wigan Evening Post. "He was very keen to do something and, although he has not played a lot, he's certainly put himself up for selection.
"In his mind he's okay, although we've got to be careful with him.
"Craig has the final say, but he is sensible. If he thought Gary would be out for months afterwards then he wouldn't want him because then he's not 100% fit."