Last year, the Nationals staff finished first in the National League with a WAR of 18.1 (via FanGraphs). That was without a full season of Stephen Strasburg and also without a single starter reaching 200 innings pitched.
Throw Dan Haren into the mix this season (in place of Edwin Jackson), and you've got yourself a ridiculous starting rotation.
They'll face competition from some other staffs for the title of "best in the National League," though.
As it's clear that the Nationals are at worst a top-five rotation, there's no need to rank teams any lower than that. This slideshow will focus on the creme de la creme—the best five rotations in the National League.