You can't really judge the MLB All-Star rosters when they are first released because they will evolve so much based on injuries. When the rosters were first released there were two Nationals who had an argument to be named a snubbed, and neither of them were selected as injury replacements. Danny Espinosa and Michael Morse will get a nice little vacation for three days, instead of heading out to Arizona for the All-Star Game.
Espinosa is one of the leading candidates for NL Rookie of the Year because of his power numbers, but he also brings excellent defense to the second base position. He is hitting just .242, but he has 16 home runs, 15 doubles and 52 rbi. I would expect him to make this game very soon.
The other snub is Michale Morse, who is having a breakout season as the Nationals replacement for Adam LaRoche at first base. Morse is hitting .309 with 15 home runs and 49 rbi. His production has been unexpectd, but his above average defense at first base is the real bonus.
As you probably know, the Nats have Tyler Clippard as their lone representative in Arizona.