can rewrite first rules ?
from
http://sitename.com/media/resizer/420x218/r/sitename.com/wp-content/uploads/2013/12/image.jpg
to
http://sitename.com/media/resizer/420x218/r/2013/12/image.jpg
by removing sitename.com/wp-content/uploads
this my current htaccess :
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /media/
RewriteRule ^resizer/(.*)x(.*)/r/(.*) resizer/resize.php?src=http://$3&h=$2&w=$1&zc=0&s=1
</IfModule>
i use this method : http://code.tutsplus.com/articles/using-timthumb-with-custom-urls-for-site-optimization--wp-23607