Sure that the number of defenders will increase for the next years, with the developement of "active defending" style, like Joo Se Hyuk (n° 20), Chen Weixin (n° 23), or the young Chinese player Hou Yingchao (n° 33), that you can see playing on this video :
http://video.sundns.org/pp/games/asia/16ACSCHN_TPE1.rm
There are 7 defenders that I know in the 100 best players (maybe some others I don't know), that's still a few, but some are coming, like Gionis (n° 113), who's playing in Metz, France, and that i will see for the first time next tuesday!
