Bruins GM Peter Chiarelli has revealed that Nathan Horton's head injury is probably a mild concussion. Horton likely sustained the injury when Philadelphia's Tom Sestito blindsided him in the second period. This news is made all the more concerning by the fact that Horton was also diagnosed with a concussion during the Stanley Cup finals. Don't count on him playing on Tuesday, but after that the Bruins aren't scheduled to play until January 31st.