Mike Petraglia @Trags | 31 min 25 sec ago | Danny Ainge indicated this morning Al Horford's concussion likely came from an accidental collision with Tyler Zeller's shoulder on Oct. 31
Who called that one? Report for TPs 
I'm having a hard time picturing how Horford (or anyone) could get a concussion from a collision with somebody's shoulder. Elbow, head, knee, kick, punch, I can understand, but shoulder? Can someone draw me a diagram or something?