Chad Billingsley' slider was a valuable pitch for the right-hander last season. He also throws a cutter and the two pitches can sometimes be mistaken for one another. But last season, his slider showed more downward movement than in the past, something that seemed to have benefited him.
The average downward velocity on his slider increased 3.7 feet per second from 2009 to 2010. His K-rate and expected K-rate jumped from his 2009 numbers. It looks like he wasn't getting as good a result on the pitch in 2009 as compared to the year before. Perhaps a slight change in his mechanics in 2010 increased the downward movement on the pitch, or he may have scrapped his approach altogether and went with something completely new. Whatever it was, it seems to be working as batters were striking out more on the pitch.