ERA Adjustment Chart
Adjustments for Pitcher Walks

One of the first things you probably figured out with the ERA Adjustment chart is that if you have two pitchers that have the same ERA, one who walked very few batters, and one who walked alot of batters, the one who walked alot, since his ERA is the same, gives up the same number of hits as the other pitcher, so can't come close to matching the other pitcher's ERA. There is simply too great a difference in the total base runners over the course of a season.

Ron Brendel developed the following chart to adjust the pitcher's ERA to compensate for a high or low walk rating. This should help even out the pitcherss base runners allowed totals for a better individualized performance. Look in the BB column for the pitcher's walk rating, and then look at the entry directly to the right for the adjustment to make to a pitcher's ERA in the ERA Adjustment Chart.

BB ERA BB ERA BB ERA BB ERA BB ERA BB ERA
1-1-1 +0.71 1-2-1 +0.44 1-3-1 +0.22 1-4-1 -0.02 1-5-1 -0.25 1-6-1 -0.49
1-1-2 +0.65 1-2-2 +0.41 1-3-2 +0.18 1-4-2 -0.06 1-5-2 -0.29 1-6-2 -0.53
1-1-3 +0.61 1-2-3 +0.37 1-3-3 +0.14 1-4-3 -0.10 1-5-3 -0.33 1-6-3 -0.57
1-1-4 +0.57 1-2-4 +0.33 1-3-4 +0.10 1-4-4 -0.14 1-5-4 -0.37 1-6-4 -0.61
1-1-5 +0.53 1-2-5 +0.29 1-3-5 +0.06 1-4-5 -0.18 1-5-5 -0.41 1-6-5 -0.65
1-1-6 +0.49 1-2-6 +0.26 1-3-6 +0.02 1-4-6 -0.22 1-5-6 -0.45 1-6-6 -0.69

So, as examples:

Let's look at the 1952 Boston Red Sox and Mickey McDermott and Mel Parnell. Mickey had a 3.72 ERA, and Mel a 3.62 ERA. Looking up their ERAs in the 1952 ERA Adjustment Chart, we find that Mickey is "no change" and Mel is (just barely) a -1 on singles. Here's the relative stats to look at:

Pitcher            H/9  BB/9  BR/9

Parnell           8.71  3.74 12.45

McDermott         7.72  5.11 12.83

As you can see, there's a good reason why Parnell had just barely a better ERA than McDermott, since he allowed fewer base runners per 9. However, in the "off-the-shelf" model, these two pitchers will allow nearly the same number of hits. In fact, Parnell, who allowed MORE hits/9 than McDermott will allow slightly less than McDermott. BUT, they will replicate their BBs/9. Thus, Parnell has a bigger advantage and will more easily replicate his ERA. If you use the ERA Adjustment innovation, Parnell calculates to an adjusted ERA of 3.64, based on his BB rating of 1-3-6, whereas McDermott will calculate to an adjusted ERA of 3.47, based on his BB rating of 1-5-1. Thus, Parnell now does not adjust hits at all, as he now falls in the "no change" range for the 1952 ERA Adjustment Chart, and McDermott becomes a -2 on singles and -1 on doubles. Thus, McDermott will allow fewer hits now than Parnell, and both pitchers should more closely replicate their ERAs.

Note: A form of the data in this chart will be included in calculations for the Advanced Game ratings. The chart will "slide" adjustments based on the average walk rating for each season. A new column, called "Adjusted ERA" will be listed on the Advanced Game ratings in the place of the current ERA column found in the expanded and traditonal ratings.

Special thanks to Tom O'Toole for passing this along.

Rev 1.0 - 5/13/99