Friday, September 04, 2009

Nathan's Slider

Manager Ron Gardenhire, faced with a barrage of questions about Nathan's sudden struggles, said Nathan "dropped his arm" throwing a nothing slider to Konerko for the tying homer. That means Nathan released the pitch lower than the normal apex of his delivery, a common mistake that reduces the sharpness of the break. A slider with little break, thrown to a power hitter like Konerko, often ends up in the seats. Gardenhire said when he removed Nathan, catcher Mike Redmond told him Nathan was dropping his arm.
Nathan vehemently denied that he was dropping his arm for any sliders to the media following the outing.  As Borzi reported, Nathan told the media members that he had noticed himself doing that several appearances ago but had made the adjustments to correct that.  A quick review of Wednesday's release points at shows that Nathan was indeed lowering his release point for several of his sliders:

This decrease has led to more horizontally breaking sliders with less vertical break.  Not only was this flatter slider was proven to be more hittable -- thanks Mr. Konerko -- but it became increasingly more difficult to locate for a strike. 
As you can see in the graph below extracted from his July 18th appearance against the Texas Rangers, Nathan's slider release was much closer to that of his fastball (small sample size notwithstanding). 
The difference between the two release points is evident in the direction the pitch is moving.   The slider from September 2nd has a more pronounced horizontal break while the July 18th version enjoys a sizable vertical break advantage:
Nathan's Slider Movement

Number of pitches

Horizontal Movement on Average (in inches)

Vertical Movement on Average (in inches)

July 18th




Sept 2nd




All of this seems to be traced back to his blown save-turned-win against Kansas City on August 21st when he threw 53-pitches.  Prior to that date, Nathan had worked 46.2 innings, accumulating a 5.45 K/BB ratio and an opponent slugging percentage of .245.  Since that outing versus the Royals Nathan has tossed 6.2 innings and seen his K/BB ratio plummet to 1.50 and his opponents slug a Pujolsian .700.  Physically or mentally, something went wrong from that date forward. 
The biggest aspect of his game to be impacted was his slider.  Before August 21st, Nathan threw his slider in the zone nearly 40 percent of the time.  While it received plenty of swing and misses both in and out of the zone, getting contact on the pitch typically meant a ground out.   However from August 21st onward, Nathan located his slider in the zone just 20 percent of the time.  As the White Sox proved so eloquently on Wednesday, is that if you can refrain from chasing it, he would not throw it for a strike.  Throwing 16 sliders against the White Sox, the opposing batters took just two of those for strikes.  The overall toll resulted in more pitches. 
There are two hypotheses that come to mind regarding this slider.  The first is that Nathan's arm is tired.  Though it is not represented in the velocity, Nathan is allowing his arm to drag a bit and thus falling to the side on the slider a tad more.  Considering the gaudy pitch totals in the month of August let alone a six-game stretch in which he chucked 163-pitches (no where else during the season did he encroach this number at all in that little of work), it is a rather easy jump to conclude that he would drift from fatigue.  The second theory is that he is INTENTIONALLY throwing more out of the zone with his slider.  After the game against Chicago, Nathan felt that he was getting "too predictable".  As a pitcher that has gone to lengths to add another pitch in recent years, Nathan is always trying to stay a step ahead so it seems.  Just a few outings prior, the Rangers' David Murphy brought Texas within one on a ground-rule double from a Nathan slider.  A week before that, the Royals' Bryan Pena tied the game on a home run off a slider as well.  To change it up, Nathan perhaps has tried too hard to locate that pitch away from a swing -- to avoid any major contact.  
Either way, fatigue-related or over-thinking, Nathan has proven himself as one of the top-notch closers in the game.  A chain of outings like this is more likely temporary than anything else.