The Nationals plan to call up Adon from Triple-A Rochester to start the first game of Friday's doubleheader with the Phillies, Jesse Dougherty of The Washington Post reports.
Washington is likely to designate Adon as its 27th man for the twin bill, so he's expected to be returned to Rochester immediately after the spot start. He'll be rejoining the Nationals after going 1-10 while supplying a 6.95 ERA, 1.76 WHIP and 44:35 K:BB in 55.2 innings over 12 starts before being demoted to Triple-A earlier this month.