From the earliest days of competition, the thought has been that negative feelings toward an opponent would only help motivate a person to defeat them. Storied athletic rivalries are often accompanied by stories of bitter feelings and outright hostility (i.e. Ali-Frazier, Belicheck-Mangini, Brett Favre-Aaron Rogers) or even mutual respect can have some tense moments (Nicklaus-Palmer, Connors-McEnroe, etc.).
But what happens when two rivals are friends -- even buddies? What if one is arguably the greatest golfer ever and the other is the most potent threat to threaten the top records in the sport?
CNN's Gary Morley has an interesting take.