Best buddies? – Tiger Woods, right, congratulates Rory McIlroy after Europe's remarkable victory over the U.S. on the final day of the 2012 Ryder Cup in September. The two are big rivals on the golf course, but a friendship has also blossomed this year.
Too close? – Golf great Nick Faldo has questioned whether they should be so close. Sports psychologist Dan Abrahams says they would benefit from keeping a bit of distance. "In the heat of battle it becomes more difficult to emotionally detach yourself from that person's performance if you're good friends with that person," he told CNN.
Beating your idol – McIlroy has admitted idolizing Woods as a boy, but has now usurped him as golf's No. 1. "Once they step on the first tee, those competitive juices are flowing and they're focused either on their own game or beating each other," Abrahams said.
Nicklaus vs. Palmer – They are following in golf's great tradition of rivalries -- most notably Jack Nicklaus, left, and Arnold Palmer. "The power of the mind and the capability of that mental discipline is what separates the good from the great," sports leadership expert Khoi Tu told CNN. "That might allow them to become friends with people off the course, but not on the course."