Aaron Heilman – Season Analysis 2008 

Basic Stats 

After looking at some of our starting pitching the past three weeks, it’s time to look at some members from the weakest part of the Mets for the past two seasons, the bullpen.  First up, we take a look at a member of the bullpen who was huge for us in 2006 but has tailed off since then, Aaron Heilman.

There’s really no other word to describe Heilman in 2008 other then awful.  He posted a 5.21 ERA after posting a 3.62 in 2006 and a 3.03 in 2007.  There have been some alarming characteristics of Heilman that might have predicted a drop in performance from him.  Coming into 2008, his strikeout rate has decreased in each year from 2005 to 2007.  Surprisingly, his K-rate took a turn for the better in 2008.  Heilman struck out 80 batters in 76 innings for a K/9 of 9.47, by far the highest mark in his career.  Unfortunately, his other peripheral stats were not good at all.  His BB/9 was 5.45, the highest mark since his 2003 season and the 2^nd highest rate in the NL this season for pitchers with over 60 innings pitched.  You simply cannot be a good reliever when you are walking batters at a higher rate than Oliver Perez.  Another problem from Heilman is the increased HR rate in each of the last three years.  Walking batters, producing less ground balls, and giving up more long balls is a recipe for disaster.  On the bright side his BABIP was .326 suggesting that he was indeed a bit unlucky this season when he batters did put the ball into play.

Another alarming thing about Heilman is that he seems to produce worse in higher leverage situations.  Although producing a 3.03 ERA in 2007, his WPA was -0.71.  In 2008, it was even worse producing a WPA of -1.69.  For those that do not like WPA, baseball-reference does a good job breaking down the numbers between high, medium and low leverage.  In 2008, Heilman OPS against in high-leverage situations was 1.006, just awful compared to the .772 OPS against in medium leverage and .644 OPS against in low leverage situations.  In 2007, it wasn’t as bad but he was still much worse in high leverage situations (.872 vs. .624 medium and .470 in low).  Unless this changes, I simply do not have any faith using Heilman as a 7^th inning or 8^th inning guy at this point.

Aside from the walks, another problem was his numbers against left-handed batters.  Lefties OPS against Heilman were .991 (vs. Righties who were at .652).  Heilman’s career numbers were .766 against lefties and .661 against righties.  So Heilman in 2008 was pretty much career average against the righties but was awful against lefties.  Later in this article, I will give reasons as to why this change likely occurred as well as perhaps why Heilman’s K/9 has increased this season.

Pitch F/X Data

 1) What Does He Throw

Using data from MLB Gameday application, we can look further in detail to what Aaron Heilman threw in 2008.  Aaron threw 1489 pitches during the 2008 season, of these gameday has tracked 1398 pitches.

Similar to John Maine, Aaron only has one type of fastball (at least that’s all I can tell from the data).  However, unlike John Maine, Aaron fastball of choice is the 2-seam fastball.  Aaron has great velocity on this pitch, throwing it a shade above 94 mph.  Another thing is the amount of horizontal movement he receives on this pitch.  Heilman throws the ball with a low 3/4ths delivery so that might be the reason for the large horizontal movement.  Although Aaron has produced his lowest GB rate of his career this season, his fastball still has plenty of sink compared to the MLB average. 

The second pitch that Aaron uses is the changeup.  Looking at various scouting reports, he actually calls this pitch a split-fingered fastball or splitter.  Contrary to the name, the split-fingered fastball isn’t really a fastball at all.  The pitch was developed by Fred Martin.  He named it such to confuse hitters into thinking that it actually was a fastball.  As the ball is released, it looks like a fastball.  Then once the ball hits home plate, the bottom drops out.  Changeup’s and Splitters are very similar to one another.  Looking at the Fangraphs data on Heilman, they classify this pitch as a changeup.  Splitters typically have more vertical movement and less horizontal movement, although again the difference might be because of his 3/4ths delivery.  On second thought, changeups usually have MORE horizontal movement then the fastball so maybe this is indeed a splitter.  As you can see, his movement on his changeup is very similar to his 2-seamer.  The difference between the fastball and changeup in terms of speeds is also very good, with a difference between the two about 10.5 mph.  But as you can see later on, Aaron’s changeup got hammered this year, especially by lefties. 

This season, after throwing hardly any last year, Aaron began using his slider as a third pitch.  I can see Aaron using this pitch more often as he has above movement on it compared to the MLB average.  I was also curious to see if the addition of the slider had helped him with his K rate.  I broke down the data into lefties and righties groups.  He ended up striking out the lefties at a LOWER rate than his career average; however he struck out righties at a MUCH HIGHER rate than career average.  He was definitely using the slider against righties to strike them out.  As a result, I can definitely see Aaron using his slider against righties even more next season.

2) When Does He Throw It?

Next lets breakdown Aaron’s pitches between Lefty vs Righty

Last season, Heilman had a big spike in K/9 in large part due to his ability to strike out right handed batters at a rate in which he has never done before.  I firmly believe the use of the slider was a major part of this.  Heilman threw the slider a bit in 2005 and 2006 before basically scrapping it in 2007.  Each year saw declining strikeout rates so that might be the reason Heilman started throwing it yet again.  I don’t have pitch by data count, but just from eyeballing it, he definitely used the slider when he was ahead in the count as a strikeout pitch against righties.  With lefties, he was primarily a fastball/changeup pitcher.  Typically using changeups are successful against opposite handed hitters.  Maybe looking at the ball/strike data below will give us some insight on why this was so ineffective against all hitters.  

3) What Happens When He Throws It?

Here is a breakdown on what happens when Aaron throws each type of pitch.  I will begin by giving total data and then I’ll breakdown the data between lefties and righties.

 Total 

Here we see that when batters put the changeup in play, it was bad news for Heilman (BABIP .327).  Not only that but the fastball was hit hard as well (BABIP .345).  Although the slider was only put into play 23 times, it was by far his most effective pitch this season.  Now let’s look at lefties and righties.

 Lefties 

Wow.  Against lefties, when the ball was put into play, the changeup and sinker was absolutely crushed.  The good news is that a BABIP that high is generally unsustainable and will revert to around .300 in the future.  Two thoughts come to mind when I see this.  For the ball to be consistently hit that hard Heilman may have been tipping his pitches or he was locating extremely poorly.  I tend to think it’s the latter.  Here’s the data for the righties.

 Righties

Here we find that against the lefties, nothing worked and against the righties, the changeup and slider were effective but the sinker was still hit hard.  Let’s see if Heilman’s ball/strike data gives us any insight on why these pitches were so ineffective.

 4) Percentage of Strikes Thrown Per Pitch Type 

Let’s see how Aaron Heilman did as far as controlling his pitches go.  Remember the average strike percentage for fastball and slider are 64% and the average strike percentage for curveball and changeup are 60%.    

I know Aaron has had a rough year this season and I been pretty vocal in expressing my anger in threads about it but I’m going to focus on the bright spots here.  He is still under the Mets control and I don’t think it would make sense to trade him right now since his value would be at its lowest point.  The increased usage of the slider against righties should help him remain his very high K/9 rate.  I really believe the walks will go down.  His rate this season was nowhere near in line with this career average.  Also, his BABIP was extremely high.  He very likely will not be as bad in 2009 as he was in 2008.  And while there’s this whole debate on clutch and whether or not it exists and if so to what kind of effect, every Mets fan knows that some players come to New York and just do not perform under the pressure.  I’m beginning to think that Heilman is one of these players.  If Heilman is on the Mets in 2009, I do not want to see him in a setup role at all.  I’d use him in low to mid leverage situations.  Keeping him in that kind of role, I do believe Heilman can give us some production in 2009 and beyond.