The Pirates have acquired Class A+ reliever Eliecer Cardenas from the Atlanta Braves as the player to be named in return for Matt Diaz. That's pretty nifty, given that Diaz was worthless and that Cardenas has struck out 75 batters in 56.2 innings at Lynchburg this year. He also walked 29, which is too many, and he allows a bunch of fly balls, but still, he has been almost unhittable, with just 31 hits.
The Braves got him in the Class AAA portion of the Rule 5 draft last year, from the Twins. He immediately took a big leap forward in the Braves system, and he's still only 23, so it's a little surprising they would give him up for so little. I can't find many reliable reports on his stuff, but the reports I have been able to dig up suggest he's a hard thrower, which makes sense, given his strikeout and walk totals. He sounds like he could be a legitimate prospect if his control improves a little bit.
UPDATE: The more I look around on Cardenas, the more it appears that he's racking up all those strikeouts with good breaking stuff, rather than with his fastball. That might not work quite as well at the higher levels. I'd still much rather have him than Diaz, obviously.