The Graf/Hingis rivalry
I find this an interesting rivalry. Steffi leads 7-2, but they had some close matches, most notably the 1999 French Open final. However, it seems that Hingis never really got her head around Graf's game. Hingis has dominant records over people like Seles and Sanchez Vicario; she didn't have a problem with most of the older generation. And although many talk about her being powered out of the women's game, she is still a combined 17-17 against the Williams sisters.
So what was it about Graf that gave her only 2 victories in 9 matches?