Every free agent pitcher carries risk. Most quality pitchers don't hit free agency until their late 20's to early 30's.
The Nats are trying to draft as many pitchers as possible so that they don't have to go to free agency. Personally, I'd take a shot at Wilson depending on his price and Wandy as well if he hits waivers. Both would slot in well around Stras and JZ.
If I had my choice I'd sign Wilson and then take a shot at Greinke after next year.
Can you imagine a rotation of SS, JZ, Greinke & Wilson? By the beginning of 2013 we would probably have a couple of guys who have earned that fifth spot.