Getty Al Horford, formerly of the Boston Celtics. The Golden State Warriors now have serious reason to sweat the possibility they may lose former Boston Celtics center Al Horford to a competing franchise in free agency. Marc J. Spears of Andscape appeared on the Monday, July 14 edition of “NBA Today” on ESPN and named three other teams that pose a threat to the Warriors’ acquisition of Horford. Golden State, obviously, expected him to sign last week. He didn’t. The [Los Angeles] Lakers ,