With the way Ross Detwiler performed in 2012 the Nationals are not looking for a great starting pitcher or even a good one. What they are looking for is a back of the rotation starter who can give them innings and keep them in games. Anibal Sanchez has the overall numbers of that type of pitcher having pitched at least 195 innings the last three seasons, and his 3.75 ERA is more of a mid rotation number than a back of a rotation number. The overall numbers of Anibal Sanchez don't tell the full story of Anibal Sanchez.
Sanchez is a pitcher capable of throwing a no-hitter. One who can look completely dominant, but he is also a pitcher that can completely blow up. Replacing Edwin Jackson with Anibal Sanchez is, in a way, replacing Edwin Jackson with a younger better version of Edwin Jackson, and the problem with the Nationals situation is that while they need a fifth starter there exist teams like the Royals and Orioles who may very well be willing to pay Anibal Sanchez like a top to mid rotation starter.