Well, the top players will most likely be playing in the finals or late in the tourney the previous week in a tournament so it would be kind of hard for them, if they are playing back to back tourneys, to travel to another part of the world in 1 day, get used to the site, and get used to the time there because of jetlag.
azarenka - pavlyuchenkova - li - jankovic
garcia - bencic - paszek - rus - kanepi - kuznetsova - stephens
bouchard - karatantcheva - larcher de brito - voegele - lim - mladenovic
mary pierce - forever #1
vaidisova - kournikova - golovin - henin
the boys - federer - gasquet - del potro - haase - nishikori