Cuz by the time the Rogers Cup is done, everyone is all burned out and lots of upsets occur at Cincy and u have lot of players not "showing" up. example, the big 3 didn't win this event.
Djokovic and Murray made the final this year
Federer made the final last year and both Fed and Djokovic made the final in 2009
Nadal is the only one who can't win Cincy, and even he made the semifinals before.