The Sun's Dan Connolly says it best, per twitter:
Who is Clay Rapada? Last seen not pitching particularly effectively against the Yankees in the ALCS, the lefty is a former Tiger, Ranger, and Cub who held all 21 left-handed batters he faced in 2010 to a paltry .195 OPS with a nifty 2.75 FIP.
For his career, against lefties (I'm assuming that Rapada will be competing for the LOOGY role in the bullpen this Spring), Rapada's been "effectively wild":
Am I the only one with a growing concern over walks in the bullpen? Rapada, Kevin Gregg, Jeremy Accardo, and Mike Gonzalez all struggle with the free pass. And it's not like the AL East teams are going to pass up on the opportunity to take a free base late in a tight game.
Still, Rapada is exactly the type of arm a team should be looking for to build a bullpen around: cheap and potentially effective when used properly. Not unlike Will Ohman last year.