I think there is plenty of reason to be concerned, it is perfectly understandable. No one knows for sure, not even Tatum or the Doctors. He is probably going to be fine for the playoffs, based on what is known.
What would worry me more is if he is seen in a boot. The immobilization leads to loss of muscle conditioning, at least it did when I was in a boot. There is the time needed for whatever injury to heal, and then there is time to build back up the muscle. I have not seen or heard anything about a boot so that is good.