Larish, a competent minor-league hitter, last appeared in the big leagues in 2010 and isn't likely to do so for Pittsburgh, but this trade suggests the possibility that someone like Jake Fox who's similar to Larish is either hurt or could be headed to the Bucs (although nothing has been announced yet, and sometimes these kinds of moves happen for no reason).
A Fox promotion would make a lot of sense. The Pirates have two similar utility infielder types on their roster in Yamaico Navarro and Josh Harrison, and they really need someone who can hit, and Fox can -- not that he's any great shakes, but he can at least provide some home-run power off the bench.â†µ
You can read about this move in much more detail here. Also, a few days ago I wrote a piece about why it would be smart to promote Fox. Note that the ZiPS projection system suggests Fox would likely hit .256/.316/.444 in the majors this season, and if he did that, he'd be useful indeed.