It's definitely disturbing how bad he's been, but you do have to keep a few things in mind:
1) AFAIK he was in great shape before surgery. Being way out of shape is going to kill you when thrown to the NBA wolves for the first time, but he might just be a young kid who had surgery, didn't manage his offseason well, and got, well, fat. It's not necessarily chronic.
2) He played about 5 games equivalent in the preseason (171 minutes) and filled up the stat sheet pretty well (75 pts on 69 fga, 43 rbs, 9 threes, got to the line, 4 blk, 4 stl)
3) Someone, maybe a coach, could try running him some simple plays inside the three point line. I'm always baffled when teams take a guy who was a dominant college PF and immediately encourage him to play like a SF. Never, ever works. Takes time, if it's even the right choice at all.
4) So far the rebounding, blocks, steals all look like he'll be fine (and good).
Don't get me wrong, 1-20 is just awful, but I do think a little better coaching and a lot better conditioning, and he could look like a much different player in a few months.