Barreto was optioned to Triple-A Nashville on Tuesday.
The A's needed to clear a spot for Tuesday's starter, Frankie Montas, and Barreto was an understandable casualty, as he did not have a clear path to everyday at-bats with the big club. Barreto has a .205/.246/.386 career slash line with five home runs and two steals in 134 MLB plate appearances. To make matters worse, he has a .232 average and a 32.3 percent strikeout rate this year in the hitter-friendly Pacific Coast League.