Brock Holt is still not free enough of concussion-related symptoms to begin a rehab assignment—something the Red Sox had hoped he could start last Friday. After visiting a concussion expert in Pittsburgh, Holt has been prescribed a new medication that he's hopeful will speed his recovery and hasten his return to the Red Sox. Various media reports suggest that the new drug is eitheramantadine (also used for Parkinson’s disease), or amitriptyline (also used as an antidepressant). Both have been mentioned as regimens used by Dr. Micky Collins of the University of Pittsburgh Medical Center—and are aimed to reduce migraine headache symptoms that often accompany concussions. Stay tuned.