How Can We Measure Offensive Consistency?

With this decade in baseball winding down, a question that presents itself is: who were the most consistent and inconsistent hitters of the last decade? To answer this question, I decided to compare the standard deviations and inter-quartile ranges of several players' wOBAs from the past 10 seasons. If the process wasn't so tedious, believe me, I would have done many more. That said, this took a very long time, so only 35 of the most prominent hitters of the past decade were included. To qualify, a hitter must have had over 5000 PA since 2000. Also, for a season to be included in the analysis, the hitter must have had over 220 PA in that season. An overview of the results is shown in the chart below.



We go by IQR in this case because nearly all of the distributions are at least somewhat skewed, so IQR will be less affected by extreme outliers than standard deviation (Sx). A prime example of this is with our "most consistent hitter", Jeff Kent. According to IQR, he is by far the most consistent. Yet his Sx pegs him as merely average in terms of consistency. This discrepancy is mainly due to two seasons that fell far outside of his normal wOBA range. In 2000, his wOBA was .428, which led all Major League second basemen. This was by far his best offensive year, as his wOBA was 30 points higher than it was in any other season. For the next 7 years, however, Kent posted a wOBA between .367 and .398. He finally began to decline rapidly in 2008, when his wOBA dropped all the way down to .326 - nearly 50 points lower than his 2007 wOBA. Despite these two outlier seasons, we still can say that Kent was the most consistent hitter of the past decade.

He is followed by Mike Cameron and Torii Hunter, two outfielders who were consistently slightly above average for the past 10 years. Yet, the bottom line is that they were more consistent than stars such as Carlos Lee, Manny Ramirez, and Ichiro Suzuki (who weren't too inconsistent themselves.)

Now for the inconsistent hitters. Of the 35 in this group, Todd Helton leads the way. Don't misinterpret this as evidence against Helton's greatness as a hitter. The thing is, when you have seasons like he did in 2000, it's hard to appear consistent by any measure (this is part of the reason why Albert Pujols is ranked 25th in this group.) Such insane seasons as that are near impossible to replicate. In fact, the main difference between Helton and Pujols in this investigation is timing. Pujols has been in his prime for the majority of the past 10 years, while over the past few seasons, the decline of Todd Helton has begun.

Most of the inconsistent players in this sample are in fact in the midst of a decline. Jim Edmonds, Brian Giles, Jim Thome, Scott Rolen and others are prime examples of this.

The most consistent hitter with a median wOBA over .400 is Manny Ramirez. Whether this was done naturally, or with the help of performance enhancing drugs is a whole different conversation. Just as an interesting side note, though, the next most consistent player with a median wOBA of .400+ : Alex Rodriguez.

Hope you enjoyed this one. I'll be back next week with what will certainly be my most irrelevant post yet: playoff predictions. I guarantee, though, that there will be lots of statistics behind my educated guesses.