Why not Detwiler?

The Nationals have signed SP Edwin Jackson to a 1-year deal worth approximately $10 Mil.  Adding Jackson to a rotation of Strasburg, Zimmerman, Gonzalez, & Wang probably makes the Nationals favorites in the NL East and also creates a surplus of starting pitching. Before the signing, John Lannon & Ross Detwiler were projected to compete for the 5th spot in the rotation, but now one is expendable.

I've already read a few rumors about the Cubs potentially being interested in a Lannon for Byrd swap. It makes sense for the Nationals since they have a surplus of starting pitching and no clear cut center-fielder, but does it make sense for the Cubs? Do we need another mediocre lefty in his late twenties? Didn't we just sign Maholm?

I think the Cubs should look into acquiring Detwiler instead for three main reasons:

• Upside: Detwiler fits the post-hype profile that Epstein seems to be targeting this off-season (Stewart, Volstad, Weathers). He was a 1st round pick in 07 (6th overall) and was rated as the 2nd best lefty in that draft after David Price. Detwiler pitched well in limited innings in 2010 (2.27, 10.0,1.9,8.0) at a few minor league levels and was decent in an extended major league look (3.00, 8.6, 2.7, 5.6) in 66 innings last season. 
• Age: Not a huge difference here, but Lannon is 27 with 751 major league innings on his arm. Detwiler is 25 and has less wear on his arm (172 major league innings). He did have hip surgery in 2010, but has shown no lingering effects. 
• Cost: Lannon, as a proven commodity, should have a higher price tag then Detwiler. Detwiler is also out of options, so the Nats may be looking to move him anyway if they don't see him as a long reliever. If the Cubs are planning on moving Bryd they may be able to get a prospect as well in a Detwiler deal. I don't want to sound greedy, but Destin Hood would be a nice fit.

If the Cubs are serious about competing this year, Lannon would make more sense and would be a small upgrade at the back of the rotation. If the Cubs are looking more long-term (as I think they are), Detwiler is a guy they can slot at the top of the AAA rotation and give him some time to fine-tune his pitching skills. It also would give the Cubs a major league ready starting pitcher with upside to call up in case of injury. As a fan, I would be more excited about giving Detwiler a chance then the Sonnanstine / Lopez combo we have in reserve right now.