For example, why is Soderling seemingly a tough matchup for Ferrer while Berdych and Del Potro aren't? Why is Nadal such a problem for Berdych? Why is Haas such a problem for Nalbandian? Why is Simon such a tough guy for Federer while Hewitt isn't etc... Essentially, this thread should serve as a way to find out why certain players matchup well against others while others, who are similar, don't.