Jayson Werth looks old to me. He's 33 this year, and will be on the team with an albatross contract for 5 more seasons after this one. His contract won't run out until his age 38 season in 2017.
I'm okay with him in the corner OF in his age 34 and 35 seasons (2013 and 2014). Potentially in his age 36 season as well if he stays healthy. NOT in CF though as I've said in other threads.
But as Werth ages, the team should give serious consideration to moving him to first base. I expect that they're thinking this as well, having given him top dollar to play well into his late 30s. His legs won't stay healthy if he stays in the outfield.
This means that Michael Morse will have to either switch teams or stay in the corner OF long-term. Makes little sense to shift Morse to 1B for a couple of seasons to only switch him back to the OF when Werth gets too old to play there consistently. Morse is only 30 this year so it's feasible for him to stay in corner OF until Werth ages out of his contract, when Morse will be 35. Morse plays adequately there and has no injury problems at the moment, unlike Werth with his ankle issues. But Morse is another big man who is best suited for 1B. Morse's contract runs out after the 2013 season.
It also means Tyler Moore may need to lose weight and play in the corner OF, or be traded. If Moore drops 20 pounds, he will be an adequate corner OF. A little slow right now with the extra baggage.
The intrigue for the Nats in the coming years is clearly at the 1B and OF positions. Right now they have FOUR players (LaRoche, Morse, Werth, Moore) who are best suited, or who will be best suited, to play first base. They will have to either move some of these guys and replace them with true outfielders or work out some sort of 1B/OF platoon system to rest weary legs. The latter is unlikely since Morse, Werth, and Moore all bat right-handed. If they want to platoon at first, it makes sense to keep LaRoche around.