The Pirates have promoted Josh Harrison and Mike Zagurski. They've moved Jose Tabata to the DL with a left oblique injury, optioned Bryan Morris to Indianapolis and cleared space for Zagurski by placing Jeff Karstens on the 60-day DL.
If Tabata is hurt, then the Tabata-for-Harrison swap sort of makes sense, although I'd have preferred to see Jerry Sands, who also is optionable and has hit well recently and could have filled the Tabata role perfectly well. The Pirates now have just three real outfielders on their roster, not including Garrett Jones, which seems a little strange heading into a series that will involve the DH.
I'm not sure what the reasoning for sending Morris down might be -- maybe we'll find that out later. It's strange that the Pirates will now have three lefties in their bullpen. But it's hard to complain about it too much, because Zagurski has been spectacular for Indianapolis, whiffing 37 batters in 21 innings. He has an established track record of struggling in the majors, but with 2013 numbers like he's had, I'm fine with him getting a shot, as long as the Pirates use him against left-handed batters and aren't afraid to designate him for assignment if he's bad.
UPDATE: Zagurski had an out clause, so that's why the Pirates are promoting him.