While some are fully on board the "sign Prince" bandwagon, others are wondering why the Nats would do such a thing. They have a decent first-baseman in Adam LaRoche (assuming he's healthy), and they have a back-up plan everyone loves in moving Mike Morse to the position. Why bother with Prince?
The possible answer lies in not in what Prince is, but what the other guys available are. In the next two seasons the pickings at 1B will be slim. Next year the "prize" is probably Mike Napoli, but he appears to be in line for a contract extension. After that... a position switched 37 year old Lance Berkman? James Loney? Ty Wigginton? No long term answers here.
Before 2014, there are a couple names that might sound good but who knows who'll test the waters by then. Joey Votto looks to be the big fish. But if he re-signs (or you fail to get him) then what? A 37 year old Paul Konerko? A possibly concussed out of baseball Justin Morneau? A Kendrys Morales who hasn't played in so long because of injury baseball-reference lists him as having a "final game"?
No, if the Nats don't get Fielder, there is next to no chance they can get an impact first baseman through free agency. Trade is always a possibility but also very hard to rely on. So that becomes plan B to Bryce coming up and moving Morse. If you're looking to go on a successful run of playoff appearances you don't want your "Plan A" to be bringing up a rookie and forcing a guy exiting his prime with less than two full seasons of success in the majors to switch to a position he barely played the year before (assuming LaRoche plays out his contract). Of course, maybe Morse will repeat 2011, and maybe Bryce will tear up the minors and the majors next year. It's not the best bet, but it's certainly not a bad one. Thing is, good teams don't bet like that. Good teams bet that the guy they just signed that's awesome doesn't break his leg in a freak vegetartian food truck rodeo accident.