Well Jim Calhoun himself claimed that he could barely get into/out of his car after the post-Georgetown flight. He also said that he's "going to need some work done," which obviously means that back surgery, either now or after the season, is inevitable. He claims to be in so much pain that it prevents him from coaching.
If you aren't buying these explanation, you obviously DO think that he is faking the back injury.
There are plenty of valid criticisms of Jim Calhoun but I don't even think his biggest critic would ever accuse him of running from adversity or quitting on his teams.