Wiemer (hand) was optioned to Triple-A Rochester on Tuesday.
Wiemer suffered a hand bruise during Monday's contest against the Mets and was sent for X-rays, though his move to the minors rather than the injured list indicates it isn't a serious concern. The 27-year-old has been a surprisingly productive bat for Washington this year with a .300/.410/.529 slash line in 83 plate appearances, but he's primarily filled a part-time role and will now head to Triple-A in favor of Dylan Crews.