The starting pitching choice is Austin Voth, or Josh Tomlin followed for sure by a bevy of Atlanta relief pitchers. In other words, this is an Atlanta bullpen game.
I'll take Voth, a promising pitcher with a good history against the Braves. Voth holds a 2.70 lifetime ERA versus Atlanta in 16 2/3 innings. 
Tomlin has a 4.61 career ERA against the Nationals in eight appearances. This will be his first start since last season. Tomlin probably isn't going to pitch more than three or four innings putting the Braves' middle relievers into action. 
The Nationals' offense has picked up with a healthy Juan Soto. The blossoming superstar is batting .433 with six homers in his last eight games. Washington is averaging 7.5 runs in its last four games.