Abbott was optioned to Triple-A Rochester after Wednesday's 3-1 win over the Mariners, Jesse Dougherty of The Washington Post reports.
The 26-year-old was shifted from the rotation to the bullpen over the weekend and fired two scoreless frames Tuesday against the Mariners, but he's now headed back to Triple-A. Abbott was demoted to make room on the big-league roster for prospect Cade Cavalli, who is scheduled to make his MLB debut Friday versus the Reds.