You may remember Meyer as the key player for the Athletics in the Tim Hudson deal many years ago, but his career has been stuck in neutral since then, as he struggled over and over in Class AAA Sacramento. He seemed to improve a bit in 2007 and then had a bit of modest success when he was finally transitioned to relief - he had a decent season in the bigs with the Marlins in 2009. In 2010, though he spent most of the year back in the minors after struggling in a few innings at the big leagues and dealing with a calf injury.
He was released by the Phillies a few days ago. He'll provide minor-league depth, but it wouldn't be a shock if he performed well and earned a callup at some point, particularly given the Pirates' current dearth of good lefty relief pitching.