Adon (biceps) was transferred to the 60-day injured list Friday.
The right-hander landed on the injured list in late August due to a biceps strain, and he won't be eligible to return for the final stretch of the season. Adon made one start in eight appearances with the Nationals this year and posted a 6.75 ERA, 1.50 WHIP and 6:4 K:BB over 10.2 innings.