Switch-hitting is typically done to give the hitter the platoon advantage at the plate. If the pitcher is a lefty, the batter hits righty and if the pitcher is a righty he will hit lefty. If the player gets no platoon advantage out of it, then there is no point in switch-hitting.
In the case of Boston Red Sox outfielder Daniel Nava, he might just end up leaving the world of switch-hitters. Throughout his career he has been a much better left-handed hitter than he has been a righty. Against left-handed pitching, Nava has struggled greatly over his career and went 10-for-63 at the plate last season (.159 avg) with a .209 OBP. He did drastically better off righties as he hit .293 with a .372 OBP off of them in 300 at-bats last season.
With this in mind, Nava told Rob Bradford of WEEI that he might consider becoming a left-handed hitter exclusively.
“I have thought about it. Is it something I’m going to do? I don’t know. It’s a tough thing to do,” he said. “[Shane] Victorino did it a couple of years ago, just dropping it. It definitely runs through my head. It’s definitely something I’m considering doing, but at the same time it’s something I’ve never done. Would I even be effective lefty on lefty, or would it be better hitting against lefties from the right side. I would have to go out and give it a test run.”
This year, Nava is projected to start the year as a backup OF/1B for Boston, so such drastic splits might make tough for him to find playing time. The better he hits off of lefties, the better of he will be for playing time-- especially in the outfield.
At first base on the other hand, Mike Napoli isn't the best against right-handed pitching so he should be able to see some playing time there regardless of whether or not he is a switch-hitter.