Sunday, April 17, 2011

Nathan's slider could use some work


The sobering reality set in on Saturday afternoon when Joe Nathan blew his second save opportunity in as many tries, forcing Ron Gardenhire to strip him of the team’s ceremonial position of closer.

Overall, the numbers resembled nothing from his pre-surgery performance. Whereas pre-Tommy John Nathan was one of the game’s best relievers, demonstrating a well-balanced repertoire of equal parts precision and power, the post-op Nathan has failed to get ahead of hitters, unable to get them to chase much out of the strike zone and miss any bats:


First-Pitch Strike%
Contract%
Chase%
Swinging Strike%
2008
63.6
70.0
30.3
14.0
2009
63.8
68.7
32.9
14.8
2011
48.2
90.7
20.3
4.6

This led to an increase in walks, hits, base-runners, Johnny Damon-walk-offs-and-celebrating–in-only-the-douchebaggery-way-he-can and disappointment among the coaching staff when Nathan has been unable to solidify a Twins victory.

Despite issues with his ability to command all pitches across the board, according to Tom Pelissero of 1500ESPN, Gardenhire attributed most of Nathan’s reduction in whiffs to the lack of bite on his slider, his once-premier pitch:
"It's that slider that's not snapping like it was, and that's the one he used to get people to swing and miss at an awful lot. Now he's kind of gone to a little bit of a curveball, because his slider is still not there yet. And that's probably par for the course with the elbow thing like that."
As I discussed at the beginning of the month, Nathan’s slider is his money-maker. Just look at some of his numbers he put up when using the pitch:
“According to Inside Edge's data, from 2007 to 2009, opponents managed to hit just .163/.205/.234 (AVG/OBP/SLG) off of his slider. Twins infielders would regularly get a quick breeze in their directions as opponents swung-and-missed a whopping 40.8 percent of the time when taking a cut. For Nathan, his slider was his go-to out-pitch racking up 122 of his 242 strikeouts on it. When hitters did make contact, the slider was typically kept on the ground – a stark contrast to his fastball which they tended to elevate.
Comparatively, while only throwing a couple of handfuls of sliders this season, the results on the pitch have been atrocious:

Joe Nathan’s slider performance

Well-Hit Avg.
In Play%
Chase%
Miss%
2009
.138
26.0
45.0
44.0
2011
.443
60.0
11.0
10.0
League Avg
.131
36.4
30.5
31.0
       (MyInsideEdge.com)

There are some schools of thought that suggest a bad slider is worse than almost any other type of bad pitch. According to an article from The Sporting News dated back in 1994 (is it still okay to cite something written when Ace of Base was topping the charts?) discussing the topic, where a hanging curveball has the advantage of having a gap in velocity, a bad slider is thrown on the same plane as a fastball and comes in at near-identical velocity. In Nathan’s case, where the ’09 slider had a six mile per hour differential from the fastball, since then just three miles per hour separate his slider from his fastball.

Using pitch f/x we see two realities of Nathan’s pre-Tommy John and post-Tommy John sliders. The first is that, on average, his slider isn’t finishing down in the zone as it did in the past. According to data found at pitchfx.texasleaguers.com, Nathan’s movement on his slider isn’t witnessing the same amount of vertical spin as it did in the past:

Joe Nathan’s slider movement

Vertical
Hortizonal
2009
2.29
1.17
2011
4.43
1.79

To better understand those numbers, the first column represents a measurement in inches of how much, on average, the pitch moves downward. More simply: the lower the number, the greater the drop. The second column represents the east-west movement. As the numbers increase away from zero and the negative numbers, this means the pitch is moving towards the pitcher’s left – or in at a left-handed batter. Knowing this, we can glean that Nathan’s slider has reminded up in the zone more frequently this year thereby confirming Gardenhire’s statement regarding a lack of bite. In essence, his 2011 slider is remaining closer to the same vertical plane as his fastball.

The second thing that pitch f/x data shows us is that, on average, Nathan’s release point on his slider has sank somewhat:


This lil’ factoid is likely the root cause of Nathan’s loss of vertical movement.

What this shows us is that in 2009, Nathan demonstrated a greater ability to stay on top of the baseball when chucking his slider. By staying on top, he was able to gain downward movement rather than an increase in horizontal deflection. This season - possibly because of the extended time off or simply because of the re-built elbow - Nathan’s slider release point has been lower compared to his ’09 outings and with it his slider has remained up in the zone.

Without question, it is easier said than done telling someone to stay on top of a pitch – particularly when there are physical influences such as a new elbow factored in. However, while demoted down the ranks of the bullpen and consuming low leverage innings, in those outings Nathan should be very conscious of where he is releasing his slider and attempt to rediscover that release point. 

4 comments:

DZA said...

Do you know how reliable the vertical/horizontal movement and release point data is across multiple years? I recall reading somewhere (fangraphs, I think) that changes in pitch f/x from year-to-year made these numbers noisier than velocity or pitch type, but wasn't sure if that was the case in general, or just for the fangraphs data.

Twins Fan c.1981 said...

@DZA

Good question and you are right about the pitch movement being volatile.

Pitch movements fluctuate some from season-to-season and stadium-to-stadium. Because of that, I wouldn't base an entire analysis on that fact alone, but it's clear in Nathan's case that his slider is staying up in the zone.

Release point is a bit different and is a little more static than the movement average from year to year but again, it does have some fluctuation based on the stadium. In Nathan's case, I saw a very similar release points for his fastball and curveball from '09 and '11 but the slider had a different point of "release"*.

*In the pitch f/x system, the "release point" is capture 50 feet away from home plate -- or 3-to-4 feet after a pitcher lets go of the ball.

I hope that addressed your question.

DZA said...

@Twins Fan c.1981

Thanks much. I hope my question didn't come across as questioning your conclusions, it was just something I was wondering about with respect to those specific measures - excellent analysis.

len said...

I suppose you are going to tell us smoking is bad too.