The 28 year old Scottish international underwent two hip operations in the summer and has been undergoing rehabilitation for the operations since. He is now hoping to be back in early October and well ahead of schedule.
Speaking to the club's official website Caldwell said: "I've been training with the lads for the past week doing football stuff day in and day out, said Caldwell.
"That's pretty good progress but I'm still not up to full speed for where I would like to be so I'm probably still a couple of weeks away from actually playing in games.
"I'm well ahead of schedule in terms of where I thought I would be at this time but although I'm back training I'm still a way off being able to play in games. There's stiffness and the mobility is still not quite there but still well ahead of schedule and still working hard to try and get back to playing games."
Although he is keen not to put a definite date on his return, Caldwell is said to be targetting early October as a potential return to first team action.