Over the last three season, Jorge del la Rosa (COL) cut both his batting average allowed and his on-base percentage allowed by over 10 points per season. His .262 BA allowed in 2008 is down to .221 in 2011. His OBP dropped from .349 to .302 in the same time period. The slugging percentage against him was sticky, however. From 2008 through 2010, it stayed between .410 and .413. Even though batters were collecting hits less frequently, the hits they were producing tended to be longer. So far in 2011, however, de la Rosa's slugging percentage allowed is a mere .343. The drop is tied to the perfection of his change up.
Jorge uses three main pitches, a fastball, slider and change up. In 2008, the change wasn't used very much, and it was tough to distinguish it from the slider.
The red area denotes his fastball, the green the slider and change up. This graph shows the maximum deflection from a straight line of the pitches. The center of mass of the slider is closest to the center of the graph, while the change up tends to be underneath the fastball.
In 2009, the slider and the change up start to differentiate, but de la Rosa is throwing the slider more than twice as often as the change.
In 2010, he shifts away from the slider to the change up as his main off speed pitch, but he's still throwing his fast ball the majority of the time.
This season, the slider is an after thought, and the change is thrown almost on par with the fastball. Here's why:
|Pitch type||SLUG 2008||SLUG 2009||SLUG 2010||SLUG 2011|
Hitters smash Jorge's fastball. In 2009, they started hitting the slider better, but as de la Rosa improved the change up, hitters rewarded him with less power. His change up made the slider better as well, as he can pick and choose his spots to use the pitch. Jorge presents a nice example of developing a pitch, then changing his patterns to use it as a new weapon.