The Red Sox are in search of a left-handed hitting backup for first base. We know this, the reporters know this, baseball knows this. So far, however, the search has turned up empty, leading some locals to look inward, rather than outward. Specifically, there've been quite a few people asking "why not Daniel Nava?"
Nava himself is not oblivious to this idea, and has spoken about the possibility, saying that the team has not contacted him about making such a move, but that he would be open to it. No surprise there--Nava has always been the guy who will do whatever is asked of him if it gets him closer to playing baseball, all the way back to acting as equipment manager at Santa Clara. Also no surprise that the Red Sox haven't asked. After all, moving Nava to first base wouldn't really fix the problem. It'd just change it.
At the moment, the Red Sox have a platoon in left. Ideally not a half-baked "Jonny Gomes for 8 games, Daniel Nava for 1" platoon, but a full-on lefty-righty platoon. Jonny Gomes is a lot better against lefties than righties, Daniel Nava is a lot better against righties than lefties. It's not exactly a riddle how this should play out.
Now, let's say Daniel Nava is acting as the backup first baseman. When do you want to have him playing that particular part? Presumably not when Mike Napoli would get to take at-bats against lefties, right? Well, in that case he'd be playing first against the occasional RHP, meaning Jonny Gomes would be seeing those same RHP, meaning we would need a backup left fielder who can hit RHP, meaning we're more or less back where we started.
The major difference? We'd have that many games with a backup first baseman lacking any experience fielding the position, rather than that many more games with a left fielder who showed some pretty solid improvement with the glove in 2012.
What this does mean is that if some left-handed outfielder--ideally one who can play right and left--suddenly appears on the market, the Sox have the flexibility to make that work on some level. Otherwise, though, they're probably just filling one hole by opening another, and probably losing value in the process.