It makes more sense to give him a break in September, as you can fill in with Thorpe, Smeltzer, or whomever and not worry about fiddling with the roster.
And no need for the IL in September.
I see that, although fiddling with the roster now avoids having to go to 7 man bullpen to squeeze Buxton on, assuming Cave goes when Cruz comes back. Now, if Buxton isn't coming back until after August 31, then either works. My main point is I think Berrios needs a breather and playing against Chicago and Detroit might be a good time.