[Plugin: Redirection] Replace path only when combined with certain subfolder

I’ve been trying to achieve this rediretion after moving a blog.
The old blog was in a physical path called blog and had many images in a directory path that begins with blog/files/….

So I’m trying to set uop redirect to replace occurrences of blog/files/… with just files/…

It is successfully redirecting the desired files but is ALSO redirecting anything else that starts with /blog

e.g. mydomain.com/blog can’t be reached.

I’m using this as my source:
/blog/files/(.*)

And…oh…looks like in my experiments I lost the target that was at least redirecting the files properly.

So the desired source could be

blog/files/a.png
blog/files/folder/a.png

etc.

I just want it ONLY to strip out “blog/” when it is followed by files.

Thanks for any help.

http://wordpress.org/plugins/redirection/