Ziegler, a right-handed submariner, is one of the more consistent relief pitchers in the game. He's got a 2.49 ERA in his four seasons, and has held right-handed hitters to a .224 batting average. Perhaps most attractively to the Diamondbacks, Ziegler keeps his pitches down; he hasn't allowed a single home run this season, and has given up only eight homers in 231 career innings.
Like most submarine pitchers, Ziegler does have trouble with opposite-hitting hitters, and Kirk Gibson will have to treat Ziegler almost like a situational lefty (but the other way around).
The Diamondbacks, who still have designs on the National League West title, have gotten great work this season from J.J. Putz and David Hernandez, but otherwise are short on right-handed relievers, so Ziegler should fit right in.
No word yet on who the A's are getting (or would get) in this deal, but a Grade B prospect seems about right. Considering Ziegler won't pitch more than 20 innings the rest of the season.