The 26-year-old, who joined the club from Oxford United in the summer, picked up the injury in training this week.
Whittingham told The News: "It's tough on Tom. He's got a bit of bone bruising in training. His knee hyper-flexed as he landed awkwardly after jumping up for a routine header.
"So it will be a couple of weeks out for him, probably, as we need to give it a bit of time. He has not been very lucky with injuries so far."
Craddock is yet to open his account for the League Two club.