Here comes the slider

Carlos Marmol's wicked slider has resulted in a lot of fist pumps this season.

We've often heard of pitchers "adding a pitch," usually in the offseason. Sometimes a pitcher will develop a changeup or add a slider, etc. But Carlos Marmol has become more effective this season by eliminating his curveball.

The percentage of pitches thrown by Marmol that were curveballs, since 2007*:

2007: 20%
2008: 13%
2009: 11%
2010: 3%

But his fastball percentage has actually dropped as well, from 46% in 2007 to 41% this year. So what gives? For Marmol, it's all about the slider. His slider percentages:

2007: 31%
2008: 38%
2009: 43%
2010: 56%

To give you some perspective, he throws his slider more often than all but one pitcher in baseball: Luke Gregerson of the Padres (he's having success, too, with a 1.82 ERA in 22 games). I really noticed Marmol's tendency to rely on his slider a couple weeks ago, and now that I'm looking for it, it's completely obvious that he's using his slider to set up his fastball.

This frustrated me for a while. Usually when a pitcher relies heavily on his breaking ball, it's because he's struggling to control his fastball and has no choice but to depend on his secondary pitch. But with Marmol, it almost seems that he'd rather throw his nasty slider and then surprise the hitter with a fastball. And the fact is, it's working. He has a 1.52 ERA, has converted seven of his last eight save opportunities (the only one he blew was against the Rockies when he entered the game in the eighth with the bases already loaded), and his ridiculous 17.49 K/9 is easily the highest in the majors. The all-time leader in this statistic among relievers is Brad Lidge with 12.98 K/9.

So I'm certainly not complaining any more, but it is interesting to watch a pitcher dominate with his slider the way Marmol does. The man's fastball averages 95 mph, yet he throws it just 41 percent of the time. But I'm sure most hitters in the National League--at least those who have faced him this season--would tell you they'd rather see just about anything other than that slider.

*All data courtesy of FanGraphs