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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 typeSLUG 2008SLUG 2009SLUG 2010SLUG 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.


Called Strikes out of the Strike Zone

(All 2011 games through May 16th - min. 100 pitches taken outside of the strike zone)

The first column indicates the total number of pitches the batter has taken outside of the pitchFX defined strike zone.  The second column shows what percent of taken pitches out of the strike zone were called strikes. Six New York Mets made the list - that's nearly a quarter of the top 25.  Call it the Madoff effect.  Oakland comes in second with 4 batters making the list.  The majority of these pitches are located off the outside edge of the zone as the following graphic indicates.

Called Strikes outside the Strike Zone in 2011

Here's a list of the batters that have had the least "non-strike" strikes called against them.

(All 2011 games through May 16th - min. 100 pitches taken outside of the strike zone)

It's interesting that Jeff Francoeur gets the smallest percent of bad strikes called against him.  The RHB ranks in the bottom 6% of the league in chasing pitches out of the zone.  Umpires apparently appreciate his free-swinging ways.


A Quick Look at Eric Hosmer

The Kansas City Royals called up Eric Hosmer (KCA) when Kila Ka'aihua (KCA) failed to hit in the majors this year.  Hosmer is off to a good start.  While his batting average isn't high at .242, he draws enough walks for a .333 OBP and slugs .515.

So far, pitchers work him outside:

Eric Hosmer, pitch frequency, 2011.They may not be working him far enough outside, however, as he owns the middle of the strike zone.

Eric Hosmer, in play batting average, 2011.Note his ability to hit the low pitch as well.  Eric smashes those for line drives with a higher frequency than balls in the middle of the plate.  Pitchers have another advantage going outside:

Eric Hosmer, called strike rate on taken pitches, 2011.Hosmer has shown good strike zone judgement.  He gets the calls at the top and bottom of the strike zone, but so far the outside edge belongs to the pitcher.  That's a bit unfair to the rookie.  He struck out three times on those outside strikes.  With his low number of at bats, it's one reason his batting average is low.  I hope the Royals encourage him to keep taking those pitches.  Eventually he'll get the calls, and pitchers will be forced into the strike zone where he can smack the ball.