The Evolution of Jorge de la Rosa's Change Up

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.

Jorge de la Rosa, pitch break by velocity, 2008.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.

Jorge de la Rosa, pitch break by velocity, 2009.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.

Jorge de la Rosa, pitch break by velocity, 2010.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.

Jorge de la Rosa, pitch break by velocity, 2011.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
Fastball	0.481	0.496	0.523	0.549
Change Up	0.463	0.228	0.294	0.153
Slider	0.264	0.337	0.409	0.308

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.

Added Dimensions

Aaron Gleeman notes that Jorge de la Rosa could be the Yankees back up plan if they do not sign Cliff Lee.  Both throw left-handed.  Both showed significant improvement over their career numbers since the start of the 2008 season.  Jorge is two years younger than Cliff.  De la Rosa would come at a lower cost, and the reason can be seen in the movement of his pitches.  Both pitchers see mostly right-handed batters, so the study concentrates on those hitters.

Jorge de la Rosa, pitch movement to RHB, 2008-2010Note that de la Rosa does a good job of mixing up the vertical component of his pitches.  He throws pitches (mostly fastballs) that stay up, and pitches with a big drop.  Almost all his pitches, however, move toward right-handed batters. 

Cliff Lee, pitch movement to RHB, 2008-2010

Lee adds two dimensions to his pitch movment.  His pitches not only stay up and drop, buy move left and right as well.  Lee forces batters to add two more dimensions to their thinking when trying to judge a pitch, and that makes solving the problem of hitting him much more difficult.  Lee is Kirk to de la Rosa's Khan.