BOCA RATON, Fla. — Florida Panthers center Aleksander Barkov underwent his first day of rehabilitation Thursday. As he sat at the Panthers practice facility hours before he was awarded a key to the City of Boca Raton in a private ceremony, he was casually dressed in shorts and a T-shirt, brace on his left knee, and reflected on angrily throwing his gloves down to the floor in San Jose on Oct. ...