The Nationals optioned Blankenhorn to Triple-A Rochester on Tuesday.
Blankenhorn's playing time had been trending downward throughout August, and he'll give up his spot on the 26-man roster to Joey Gallo (hamstring), who was activated from the injured list Tuesday. Blankenhorn posted a meager .317 OPS in 32 plate appearances for the Nationals but is slashing .246/.328/.518 with Rochester.