There is no question that the most talked-about topic heading into the U.S. Open is Serena Williams' Grand Slam bid. Even if she does dominate the conversation, a certain "Big Four" of men's tennis will provide plenty to discuss, too, as usual.
No. 1-seeded Novak Djokovic, for example, has been nearly as dominant as Williams in 2015. He won the Australian Open, was the runner-up at the French Open, then won Wimbledon, part of a 56-5 season that includes six titles and 10 consecutive appearances in tournament finals.
Given his excellence on hard courts, it's hard to believe he's earned the trophy only once at Flushing Meadows.