Why is it that the same people who decry the "overuse" in their minds of statistics to evaluate players are always the first ones to throw a players Batting Average out there when defending the players they like?
Some people who view themselves as "traditionalists", and eschew any form of modern performance analysis, will frequently then throw a 19th century stat at you in a debate.
For over 100 years, Batting Average has been the first measure that people have traditionally looked at when trying to gauge a players contributions on offense. Batting average, is always the first thing you see on television, the newspaper, and hear from the announcers on both TV and Radio. So it is certainly understandable why most people refer to Batting average first and foremost when trying to understand or establish a players value on offense.
However, Batting Average turns out to be a woefully inadequate and incomplete way to measure offensive value. And it's really quite simple to understand why.
1.) Batting average does not include Walks or Hit By Pitch in it's calculations.
2.) Batting average treats all hits as the same value, regardless if it's a single, double, triple or homerun.
So it is very common to see a player who might have a high batting average, but few walks and little power often be somewhat overated by many fans and even other players of the game. Heres why.
THE VALUEOF WALKS AND HBP
So...how is batting average calculated, and why doesn't it "work" as well as we thought:
Batting average is simply hits divided by at bats.
Example: 3 H / 10 AB = .300
But what is an at bat?
Well, "official at bats" do not include walks or hit by pitch. In batting average, a walk or a hit by pitch never happened.
Think about that a moment. All those walks and HBP are treated as non events by the metric called batting average. In BA these events have ZERO VALUE.
It should be obvious to almost any observer of the game that Walks and HBP have ALOT of value. Firstly, and most importantly, an out has been avoided. When you go to the plate, the first thing you are trying to do is avoid making an out. (You only get 27 in a 9 inn game of course). You also create a baserunner, (yourself) who has the potential to score later in the inning. And if there is a runner on first base, or a force at any base, those runners all advance a base. Another advantage is that the pitcher has to throw more pitches, causing him to perhaps tire earlier, and if the player who walked is the first runner on base that inning, the pitcher must then throw from the Stretch position, where many pitchers are less effective and lose velocity on their pitches to home plate. Finally, the runner now on first usually needs to be "held on". The act of the first baseman holding the runner on create an additional gap between the firstbaseman and the second baseman, making it more likely the next hitter can get a base hit.
The only difference between a walk and a single is that a forced runner cannot advance more than one base on a walk, and a non forced runner, does not advance at all.
So the old adage you heard from your little league coach was true
"A walks as good as a hit"......Well, almost as good. It has been calculated that a walk has roughtly 70% of the value of a single.
So if it walk or HBP has 70% the value of a single, doesn't it seem kind of silly to eliminate these events when evaluating a players contribution?
OF COURSE IT'S SILLY.
The solution: Use ON BASE PERCENTAGE instead
On base percentage is simply the percentage a player gets on base, regardless of how he got there. Another way to look at it is the percentage of times he avoided making an out. The formula is basically
hits plus walks plus hit by pitch, divided by at-bats plus walks plus hit by pitch
THE DIFFEREING VALUE OF HITS
The second major flaw of BA is it credits all hits the same. Clearly a homerun is worth more than a single, but batting average doesn't tell you that. Slugging percentage, however DOES.
Slugging Percentage is simply total bases divided by at bats.
Single = 1 base
Double= 2 base
Triple = 3 bases
Homer= 4 bases
Add up the total bases a player has accumulated through all his hits, and divide by at bats and you have a players slugging percentage.
In this way you can properly value the TYPE of hits a player is getting.
So, I would strongly encourage all people to rely LESS on batting average, and MORE on OBP and SLG to help them deterimine which players are making the strongest contributions on offense.
In doing so, you will certainly find that some players seem overvalued based on just their batting average, and you will also find that other players are undervalued, at least in popular perception.