The same thing that Hingis used to destroy Monica, her variety and shotmaking, is the same thing Graf could kill with her movement and her own power. Still, all their last five matches went the distance including the notorious 5 setter at 96 Chase.
btw Hingis and Graf are playing an exo in Taipei in May. Back in the day Cheeky Hingis was one of the very few players Graf really disliked. Are the cool with each other now? Hingis will be looking to get back at Graf over that 99 RG fiasco that she still can't get over even today, though I maintain it was the 2 AO's that she lost against Capriati that were worse.