.htaccess send requests to a subfolder's index.php

The answer that fixed my problem is:

RewriteEngine On

Options Indexes FollowSymLinks

RewriteBase /blog/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule !\.(js|ico|gif|jpg|png|css)$ index.php

It appears that the Multiviews was throwing it off.