According to Dwain Price (and several others on twitter), O.J. Mayo sat out of today's Blue/White scrimmage due to a laceration on his hand that he sustained when... falling down stairs?
His hand was apparently wrapped up protectively. When asked if he was ok, he responded "yeah". PROFOUND.
Also, don't read this tweet if you're easily grossed out:
There was a pretty big chunk missing in Mayo's right hand after the fall but he should be available for Monday's preseason game vs. Houston— Earl K. Sneed (@EKS_MavsNBA) October 13, 2012
So there you have it. O.J. Mayo lost a chunk of his hand falling down stairs in Spain.