Back in 2006, Jeff Sackmann wrote an article in the Hardball Times taking a look at what should be expected from each rotation spot. His research was done because people tend to overestimate how good a pitcher should be. Sackmann studied the 2006 season to find the results for each spot in the rotation, using the following method:

For the purposes of this article, it’s necessary to define exactly what a #1 starter (or #2, or #3) is. To keep things as simple as possible, I used ERA as a measure of pitching ability. I also figured that each rotation spot accounts for 32 starts. On many teams, the #1 guy isn’t the same for the whole season. For example, let’s look at the 2006 Twins. Here are all of the pitchers who made more than one start for Minnesota last year:

Starter GS ERA Liriano 16 2.16 Santana 34 2.77 Bonser 18 4.22 Radke 28 4.32 Garza 9 5.76 Silva 31 5.94 Baker 16 6.37 Lohse 8 7.07By ERA, Francisco Liriano was the best of these guys, but he only made 16 starts. So, he made half of the “#1 starter” starts. Since Johan Santana is next in line, I assigned 16 of his starts to round out a composite #1 starter. Thus, the Twins #1 starter was half Santana, half Liriano. Santana’s remaining 18 starts were assigned to the composite #2 starter.

Intuitively speaking, that distribution is a reflection of the fact that, while Liriano was in the rotation, Santana was #2. When Liriano was in the bullpen or on the disabled list, Santana was #1.

Sackmann discovered that the rotation spots broke down as follows:

Lg #1 #2 #3 #4 #5 MLB 3.60 4.14 4.58 5.10 6.24 AL 3.70 4.24 4.58 5.09 6.22 NL 3.51 4.04 4.57 5.11 6.26

Prior to the 2011 season I updated Sackmann’s research, using the exact same method he used, and looking at the 2010 results. Here were the results four years after Sackmann’s first update.

2010 update:

Lg #1 #2 #3 #4 #5 MLB 3.10 3.61 4.15 4.62 5.69 AL 3.24 3.71 4.28 4.76 5.68 NL 2.99 3.53 4.03 4.49 5.70

As you can see, the league saw drastic improvements across the board. There was almost a half run improvement at each starting spot from 2006 to 2010. That said, there was still some disconnect between an actual number four and number five starter, and what people think of as a number four and a number five starter. The opinions that people have of a back of the rotation starter are much more optimistic than the reality of what the average back of the rotation starter produces.

I have been wanting to update these numbers this year, since it has been three years since the last research. In that time, the pitching numbers have gone down once again, and I don’t need a big study to show that. Last year the average ERA in baseball was 3.87. The year before it was 4.01. The 2013 average is the lowest in baseball since the 1992 season.

I don’t know if the 2013 numbers represent a new trend, of if they represent an outlier. It might not be a good idea to base this research entirely on the 2013 season. But that’s what I’m going with for this update, to show how the numbers compare to the 2010 results, and to give an updated look at what should be expected from each rotation spot. Here are the results, by rotation spot. The 2010 results are in parenthesis.

**#1 Starter**

**MLB Average:** 2.82 (3.10)

**MLB Median:** 3.07 (3.09)

**AL Average:** 3.07 (3.24)

**NL Average:** 2.80 (2.99)

**MLB Best/Worst:** 1.83 / 4.11 (2.08 / 4.17)

**Average of the Top 15 Rotations:** 2.70 (2.84)

**Average of the Bottom 15 Rotations:** 3.17 (3.37)

**MLB Range of the 11-20 Ranked Rotations:** 2.55 – 2.91 (2.88 – 3.35)

The median didn’t change here, although the average dropped about 30 points. The average of the top rotations improved by 14 points, while the average of the bottom rotations improved by 20 points. The mid-range rankings went from 2.88-3.35 in 2010, to 2.55-2.91 this year. That means the top 20 teams all had a 2.91 ERA or better in their best 33 starts of the season.

**#2 Starter**

**MLB Average:** 3.39 (3.61)

**MLB Median:** 3.60 (3.58)

**AL Average:** 3.58 (3.71)

**NL Average:** 3.38 (3.53)

**MLB Best/Worst:** 2.69 / 4.41 (2.71 / 4.69)

**Average of the Top 15 Rotations:** 3.27 (3.31)

**Average of the Bottom 15 Rotations:** 3.69 (3.91)

**MLB Range of the 11-20 Ranked Rotations:** 3.64 – 3.80 (3.42 – 3.72)

Once again there was a change here, with the average improving by 22 points. The median once again stayed the same, and actually went up two points. Looking at the differences in the numbers, it seems that the biggest change came from the bottom 15 teams. The top teams stayed about the same, while the bottom teams saw improvements. The worst team in baseball was 28 points better than 2010, while the bottom 15 average was 22 points better.

**#3 Starter**

**MLB Average:** 3.77 (4.15)

**MLB Median:** 4.04 (4.12)

**AL Average:** 4.05 (4.28)

**NL Average:** 3.75 (4.03)

**MLB Best/Worst:** 3.01 / 5.27 (3.22 / 5.19)

**Average of the Top 15 Rotations:** 3.53 (3.73)

**Average of the Bottom 15 Rotations:** 4.26 (4.56)

**MLB Range of the 11-20 Ranked Rotations:** 3.81 – 4.18 (3.86 – 4.42)

Once again we see improvements, although this time the improvements are across the board, rather than just from the bottom 15 teams. The surprising thing here is that back in 2006, the average number one starter had a 3.60 ERA. Now, just a few points worse than that will only get you a number three starter.

**#4 Starter**

**MLB Average:** 4.32 (4.62)

**MLB Median:** 4.68 (4.57)

**AL Average:** 4.69 (4.76)

**NL Average:** 4.28 (4.49)

**MLB Best/Worst:** 3.44 / 5.89 (3.51 / 6.05)

**Average of the Top 15 Rotations:** 4.00 (4.20)

**Average of the Bottom 15 Rotations:** 4.98 (5.03)

**MLB Range of the 11-20 Ranked Rotations:** 4.14 – 4.36 (4.38 – 4.78)

In this case, we saw a bigger jump from the top 15 rotations. You could also expand that to the top 20 rotations, if you consider that the number 20 ranked team in 2013 had better production from the number four spot than the 20th best team in 2010.

**#5 Starter**

**MLB Average:** 5.54 (5.69)

**MLB Median:** 5.88 (5.69)

**AL Average:** 5.83 (5.68)

**NL Average:** 5.56 (5.70)

**MLB Best/Worst:** 4.15 / 7.51 (4.56 / 7.16)

**Average of the Top 15 Rotations:** 5.00 (5.41)

**Average of the Bottom 15 Rotations:** 6.39 (5.97)

**MLB Range of the 11-20 Ranked Rotations:** 5.45 – 6.33 (5.37 – 5.96)

Once again the results improved from 2010. However, I think the expectations are still too high for number five starters. The best team in baseball had a 4.15 ERA from their fifth best spot, but the average is a 5.54 ERA, and the average from the best rotations is a 5.00 ERA.

**Dividing Lines**

In his original article, Sackmann had dividing lines in his research, where he basically took the mid-point between each rotation spot to give a better idea of the range for each rotation spot. This can also be accomplished by getting the average of all of the pitchers for each spot (for example, the mid-point for the #1/2 starters is the average of all of the #1 and #2 pitchers). The dividing lines for 2013 (with 2010 in parenthesis):

#1/#2 – 3.21 ERA (3.36)

#2/#3 – 3.69 ERA (3.88)

#3/#4 – 4.19 ERA (4.38)

#4/#5 – 5.09 ERA (5.15)

That breaks down to the following ranges:

#1 – 3.21 ERA or better (3.36)

#2 – 3.21 – 3.69 ERA (3.36 – 3.88)

#3 – 3.69 – 4.19 ERA (3.88 – 4.38)

#4 – 4.19 – 5.09 ERA (4.38 – 5.15)

#5 – 5.09 ERA or worse (5.15+)

The quality of pitchers has gone up considerably since the original study in 2006. The dividing lines between a number one and a number two starter was a 3.87 ERA in 2006. Now the dividing lines for a number two and three starter is better than that mark.

At the same time, a back of the rotation starter still puts up an ERA around 5.00 or worse. It seems that if someone drops below a 4.19 ERA (which is the end of the range for a number three starter), he’s not considered a guy who should be in a major league rotation. A good rotation is going to have a number three quality starter at the number four spot, but is still going to have one weak starter in the rotation.

When I talk about future projections for prospects, what I’m referencing are the league averages and not where they fit in on individual teams. When I’m talking about a guy who can be a number four starter, I’m talking about an ERA in the 4.19-5.09 range. I feel like the opinion of each starting spot is usually one spot higher than the actual results. When people think about the numbers from a number four starter, they’re actually thinking of a number three starter. The numbers from a fifth starter are what people think of as a fourth starter.

Tonight I’ll take a look at what the Pirates have in their rotation, based on the above numbers.