Certainly, Marmol's biggest problem is his control. His fastball has been out of the zone more than 50% of the time, which is unusual; also, his 5.56 BB/9 is actually an improvement over 2009's ridiculous 7.91 mark. His ability to keep the ball out of play helps him in that regard, though, since he'll be more apt to strand the runners he lets reach.
Gameday PITCHf/x data is from MLB Advanced Media; it can be easily accessed via this tool.
Also, a big thanks to Harry Pavlidis and his article on pitch type benchmarks.