The Scotland international has played just one match since the beginning of April due to a hip injury.
With Maynor Figueroa, Antolin Alcaraz and Ivan Ramis already sidelined, Caldwell's return will be a huge boost to Wigan's bid to beat the drop.
"All you can do when you're out of the team is keep working hard and being ready for when the opportunity arises again," Caldwell told the Wigan Evening Post.
"Everyone in this squad has a massive role to play between now and the end of the season.
"Everyone has to be ready for when the gaffer decides it's right to go in, and that's definitely the case with me."
The Latics are five points adrift of safety with four games remaining, but Caldwell insists the club have not given up hope.
"We're looking at every game between now and the end of the season as one we have to win, and we believe we can do that," he said.
"We've been down there and managed to get out of it for the last few years, and we're bracing ourselves for it going all the way again.
"It's in our hands, and we have to have a real belief that we can still get out of it."