It has everything to do with playing a new position. A position he's unfamiliar with. A position he doesn't react instinctively to, because he hasn't played there and learned, so that he doesn't have to think about which play to make, where/when to take a cutoff, etc etc.
The idea you can just go play 2nd base, without any experience, leads to a guy going to second base on a hit to right field. Or throwing home on a tailor made DP ball that gets you out of the inning with minimal damage.