Not that I think it is likely, but one of the reasons some analysts have said the Nats should pick up another starter is to shift Detwiler back to the bullpen for the playoffs. He is death to lefties, with a ridiculous GB% (65%), a GB%:FB% ratio of 3+:1, strikes out 22% of lefties, and has a 3:1 K:BB ratio. Not that he's ineffective against righties, but he dominates lefties by most measures (he's been a bit unlucky on HR/FB). He'd be a dynamite 7th inning option, allowing us to match up L-R-L with Gonzo / Mattheus / Det and save Storen and Burnett for the 8th. He could pitch a 5th and a 6th or extra innings. He'd be taking the Gorzo role, so he'd be a clear upgrade.
I still don't think it is likely, but if Lannan were lights out, you might see him making the roster for NLCS and WS to start game 4s if the thinking were that Det in the bullpen could be a good weapon. It's basically a calculation of whether 10 -12 innings of Det in game 4s and Gorzo (or Lannan) as long men is more valuable than 10-12 innings of Lannan and Det in the pen instead of Gorzo.