Irvin (shoulder) will throw a bullpen session Tuesday, Kyle Williams of TheBanner.com reports.
The righty hurler will get back on a mound for the first time since he was shelved by a right shoulder strain in late May. Irvin has found more swings and misses this season with 58 strikeouts over 51.2 innings, but he's posted a 5.23 ERA and 1.36 WHIP. He will likely need at least one rehab start before rejoining the Nationals' active roster.