Over the course of four major league seasons, Daniel Nava has seen 337 plate appearances against left-handed pitching, taking each one from the right side of the plate. The results have been poor. His line of .209/.287/.298 stands in stark contrast to his .293/.385/.428 figure from the left side of the plate, so much so that Nava has told Rob Bradford he's considering giving up switch-hitting entirely.
Fans love to throw this idea out there for every switch-hitter who struggles from one side of the plate, but it's a far more daunting task than most realize. After all, Daniel Nava has never stood in against a major league lefty from the left side of the plate. In fact, it may well have been a decade or more since Nava last had to deal with picking up on a delivery from a same-handed pitcher. Imagine spending your entire life without seeing a lefty, and then suddenly running into your first at the highest possible level of competition.
If Nava goes down this path, there's every possibility that the results will be ugly, especially early on. Shane Victorino hitting .300/.386/.510 against righties after giving up left-handed hitting in 2013 is far from the norm. It's highly unlikely that this switch would actually improve Nava's numbers against lefties in the immediate future.
So why make the switch? Because the opportunity cost is just about non-existent.
At the moment, Nava is joined by outfielders Hanley Ramirez, Rusney Castillo, Mookie Betts, Shane Victorino, Jackie Bradley Jr., and Allen Craig on the Red Sox roster. Of those, Jackie Bradley Jr. is the only one besides Daniel Nava who hits left-handed, and given his offensive struggles it's hard to say he counts. With Ramirez, Castillo, and Betts the likely starters, and Victorino the obvious fourth, that's four players who will get the at-bats against lefties before Daniel Nava.
Against righties, however, Nava may well be able to carve out a chunk of playing time. He's still not likely to be a regular starter anytime soon, but the Red Sox have a need, and that need is left-handed hitting. Every once in a while an at-bat against a lefty may come up, but by-and-large Nava and the Red Sox don't need to concern themselves with his ability to produce in those moments. They should be too rare to have a significant impact, at least while the majority of the outfield isn't on the disabled list.
Certainly, Nava hasn't resigned himself to being a lifetime pinch-hitter. At 32 years old, he's not exactly in the prime of his youth, but this is a player who, as recently as 2013, hit .303/.385/.445 for a World Series winning team. Even in 2014 he hit .308/.379/.395 after returning to the majors once-and-for-all in June. But if ever there was a time to take the plunge and get to work hitting exclusively from the left side, this is it. Any deficiencies he has against lefties will be hidden by all the strong right-handed hitting on the team, and if there's no perfect substitute for in-game action against major league pitchers, he can at least get his work in in terms of learning how to hit lefty-on-lefty.
The upside here is probably not all that great either, mind you. Daniel Nava's numbers against righties might improve slightly as he focuses entirely on left-handed hitting, but improvement in his overall numbers will mostly come from simply not facing lefties anymore, which likely would have happened anyway in 2015. Still, if all he's risking is that .585 OPS, well, what's he got to lose?
For better than a decade now, Daniel Nava has done whatever he could to keep the baseball dream alive. Now he's faced with carving out a role in an outfield featuring a three-time All-Star, one of 2014's top prospects, and a man who was paid $72 million before he had seen his first major league at bat. Making the change from switch-hitting is a daunting task, to the point where many a player has stuck to their guns through an entire career of mediocrity from one side of the plate or another rather than try something new. But if it's a change that keeps Nava in the mix, it's hard to imagine he'll back down from the challenge.