So the Mavs are the 7th seed right now. They are just barely in it. Dirk is the heart and soul of the Mavs. Even if he is down for only 2 weeks, and how likley is that, the Mavs could easily miss the playoffs. Their current market price is $150.55. There's a pretty good chance they could lose about 8 of their last 12 games. You do have to assume Denver and Golden state will have more wins then Dallas. If Dallas gets to 50 total wins, and they don't make the playoffs, they only earn $100. Right now that will get you $50 a stock by shorting them.
I'm not 100% sure on this, but I believe market pressure effects the stock as well, so it can drop lower then $100 relative to what everyone else does with this stock. I'm not 100% on that, so don't take my word on this part. I'm still some what new to this