Everyone post here how they feel Juan Martin Del Potro was able to upset Roger Federer at the US Open '09.
Here's mine: Martina Navratilova mentioned in the fourth set of the final that Roger needed to start using his slice again. I agee with her on that, but I also feel there was an even more under-used shot. Federer has the best drop shot currently on tour. To top it off, Del Potro struggles to get droppers. Not one time did Federer use it.