Saturday, August 25, 2007

Justin Morneau: A Home Run Drought Studied...

Yes, it's 7:40pm, and I still haven't blogged yet today. You regulars are probably wondering just exactly where I've been all day. Well, I've been doing A LOT of studying of baseball statistics, trends and probabilities. Most of you that follow major league baseball know that Justin Morneau of the Minnesota Twins is one of the league's best young players. The controversial AL MVP award winner last year (many thought David Ortiz, Derek Jeter or teammate Johan Santana were more deserving), Morneau is someone who many think will someday hit 50 or more home runs in a year. At 26 years of age, growth is definitely still possible. Morneau hit 34 home runs in his MVP campaign last year, and through the games of July 23rd this year, he had hit 28 home runs. That date also happened to be the Twins' 100th game of the year, and at the time he was on pace to hit approximately 45 home runs. Since Morneau had hit nine home runs in his past 107 at bats, little did we know that a very long home run drought was about to begin...

The very next day, Morneau would go 0-for-4... The next five games, he would get red-hot, hitting .538 (9-for-17) but without a longball... A 1-for-22 (.045) slump would follow the following six games, the lone hit being a single. A 2-game hot spell against Kansas City 4-for-9 (.444) then occured... This was followed by a 2-for-20 (.100) five game stretch. Morneau's homerless drought had now reached 19 games. Perhaps even more concerning to me is that over that time he drew only one walk, while striking out 12 times. Was he pressing??? With only 16 hits in that 72 at bat stretch (.222 BA), one walk, and no homers, perhaps he was. That 45 home run projection was quickly becoming a VERY distant memory. Many people thought that perhaps he was hiding an injury...

Morneau went 3-for-10 the next two games, but once again without a walk or home run and adding three more strikeouts. On September 17th, things began to change. Morneau drew his first walk in 16 games as he went 1-for-3. Over the next six games he would go 9-for-22 (.409), while drawing six more walks, only striking out once. Still though, the home run was missing from his resume'. Morneau had gone an ENTIRE MONTH (28 games played) without a home run!!! In 104 at bats, he had tallied 28 hits for a decent .269 batting average. His on-base percentage though was only .319 and his home run-deprived slugging percentage was only .346.

And then last night (August 24th), it finally happened... Given that he had reached base in 15 of his previous 28 plate appearances (9 hits, 6 walks), I figured he might soon finally break out of his power drought... Sure enough he went 2-for-5 with his first home run in a month!!!

This all leads me back to the question... just how much out of the normal statistical probabilities was it for Morneau to go 104 at bats without a home run??? So I went off to Google some stuff on statistics and baseball. I soon stumbled upon a book online called Teaching Statistics Using Baseball by Jim Albert - who happens to be a college professor (and also a big Philadelphia Philles fan). Although only a few pages were available for viewing online, I comprehended the material so well that I wanted to see more. Unfortunately, trips to my local Barnes & Noble and Borders did not yield any copies of the book in stock. Nonetheless, I was able to take the information from some of the examples used in the book (most notably Chicago Cubs third baseman Aramis Ramirez) and apply it towards Morneau.

Prior to his recent power slump, Morneau had hit 107 home runs in his first 1830 major league at bats. A rate of one every 17.10 at bats. Some quick figuring shows that over 104 at bats, you would expect to see Morneau on average hit about six home runs. What I'll show next is a table showing the probabilites of normal statistical home run outcomes for Morneau in 104 at bats based on his prior history:

HR Chance
-- ----
0 0.19%
1 1.23%
2 3.92%
3 8.29%
4 12.99%
5 16.14%
6 16.54%
7 14.38%
8 10.83%
9 7.17%
10 4.23%

11 2.25%
12 1.08%
13 0.47%
14 0.19%
15+ 0.10%

As you would expect, the typical 104 at bat sequence by Morneau should produce 5 or 6 home runs almost a third (32.68%) of the time. Almost 95% of the time (94.48%), you would expect Morneau to hit between 2 and 10 home runs in a 104 at bat sequence. The 95% level is significant because this number represents the normal "standard deviation" in mathematical circles... Based on the above findings, if you gave Morneau 104 at bats, you would expect him to go homerless only once in 526 such periods!!! In other words, he would have to have a career of around 54,737 at bats expect this to happen once... Only a very few batters in the history of baseball have even managed to accumulate 1/6 of that number of at bats...

Thanks to a couple of nice websites, it's actually pretty easy to take Morneau's career numbers and break them into almost equal increments of around 104 at bats each (the actual numbers are between 100 and 106 at bats for each of the now 19 segments)...

06/10/03-09/26/03: 101 AB, 4 HR
09/27/03-08/03/04: 100 AB, 6 HR
08/04/04-09/03/04: 103 AB, 10 HR
09/04/04-04/25/05: 101 AB, 4 HR
04/26/05-05/25/05: 100 AB, 6 HR
05/26/05-07/04/05: 100 AB, 4 HR
07/05/05-08/08/05: 101 AB, 4 HR
08/09/05-09/10/05: 101 AB, 4 HR
09/11/05-04/12/06: 100 AB, 7 HR
04/13/06-05/17/06: 101 AB, 5 HR
05/18/06-06/18/06: 100 AB, 7 HR
06/19/06-07/21/06: 102 AB, 9 HR
07/22/06-08/18/06: 100 AB, 6 HR
08/19/06-09/16/06: 101 AB, 2 HR
09/17/06-04/16/07: 103 AB, 5 HR
04/17/07-05/16/07: 104 AB, 7 HR
05/17/07-06/16/07: 106 AB, 8 HR
06/17/07-07/23/07: 106 AB, 9 HR
07/24/07-08/23/07: 104 AB, 0 HR

The actual distribution:

HR #
-- -
0 1
1 0
2 1
3 0
4 5
5 2
6 3
7 3
8 1
9 2
10 1

Other than that recent stretch, there are no other "outliers"... one period late last year, saw a stretch of only two home runs in 101 at bats, while a stretch covering most of August 2004 and into early September of that year, saw Morneau hit 10 home runs. Given the corresponding 3.92 and 4.23% respective percentages, you would expect to see a two home run and a ten home run stretch represented. Now, while the numbers don't represent a perfect "bell curve", the majority of the occurances (13 of 19) did fall between 4 and 7 home runs, something you would expect to happen about 60% of the time... The 104 homerless at bat streak though is clearly an outlier, and not one we would expect a healthy Morneau to ever repeat in his career.


Now that I have some of COMPLETELY bored and probably VERY confused, I promise to go back to my usual fare tomorrow. :)

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