Die-hard baseball fans and numbers enthusiasts certainly enjoy having numerous ways to evaluate players.

Stats and numbers definitely add another dimension to watching baseball. However, it can be a bit overwhelming for a casual fan.

Especially since plenty of abbreviations representing different statistical categories are often quite similar and difficult to differentiate one from another.

For example, a lot of baseball fans are having difficulties distinguishing RA and ERA. To provide some help,

I’ll explain some of these confusing stats, clarify what does RA mean in baseball, and look into a couple of closely related categories such as RD and RS.

## What Does RA Mean In Baseball?

**RA, or Run Average, is a statistical category in baseball measuring the rate at which runs are allowed or scored. **

However, it’s mainly used as a defensive metric, indicating the number of runs a pitcher gives up per 9 innings.

Unlike ERA, the RA includes both earned and unearned runs. As such, it’s often referred to as the Total Run Average or TRA.

Besides evaluating pitchers’ performances, Run Average can also be used to provide insight into the team’s overall defensive performance.

In addition to giving us an overview of the pitcher’s play, RA is also significant for historical reasons.

In some leagues in the early days of baseball, such as Negro League, statisticians can only count on box score numbers.

Since there’s no data on earned runs, RA is the only way to get some sense of how pitchers in those leagues performed.

## How To Calculate RA?

Calculating Run Average or RA is pretty much straightforward.

To get RA value, all you need is the data on runs a certain pitcher has allowed and the number of innings in which that pitcher has played.

Once you have those numbers and know that a baseball game lasts 9 innings, you can calculate RA using this simple formula:

**RA = 9 x (R (Runs) / IP (Innings Pitched))**

Of course, R in this formula accounts for both earned and unearned runs.

## What Is A Good Run Average (RA) In Baseball?

As RA involves both earned and unearned runs, it will always be higher than ERA.

So, the benchmarks determining which Run Average is good in baseball are slightly higher than those used for ERA.

However, as most pitchers rarely have more than a couple of unearned runs to their name during a season, the difference between these benchmarks is usually negligible.

**So, we can say that a RA below 2.00 is exceptional and very rare. **

**Any RA between 2.00 and 3.00 is considered excellent. **

**The 3.00 – 4.00 RA is still pretty good and pitchers with those stats are viewed as above-average.**

## ERA vs RA – What’s The Difference And Which One Is Better?

I already mention that RA, unlike ERA, includes unearned runs.

Preventing opposing teams from scoring runs is the main goal of defense, and thus a shared responsibility of pitchers and fielders.

The ERA (Earned Run Average) was introduced to account for the influence that fielders’ play may have on pitchers’ performance.

However, removing unearned runs from the equation doesn’t necessarily provide the best understanding of the pitcher’s performance.

The unearned runs, even though they come from an error, are also often partially a result of the pitcher’s play.

For example, a pitcher may contribute to an unearned run by allowing an opposing runner to get to the base through a walk or hit.

RA, by including unearned runs, gives a better understanding of the pitcher’s contribution to the opposition scoring.

Still, RA also has its own shortcomings as it counts the unearned runs that are not the pitcher’s fault, such as catcher’s interference.

## What Does RD Mean In Baseball?

**RD, or Run Differential, is a cumulative team stat that is based on offensive and defensive scoring. **

**The Run Differential of a team is determined by subtracting the total number of runs allowed from the total number of runs the team has scored. **

Logically, if the team scores more runs than it allows, the RD will be positive. In the opposite case, the RD is negative.

Run Differential exists in correlation with the total number of wins and losses and can be used to determine which teams are over or underachieving.

There have been cases of teams ending the season with more wins than losses and a negative RD, but those instances are extremely rare.

However, this doesn’t mean that the team with the biggest Run Differential is necessarily the best team.

Run Differentials are also important as they can be used as tie-breakers when teams have the same win/loss records.

## How To Calculate RD?

Calculating RD is as simple as it gets.

All you have to do to determine Run Differential is subtract runs allowed from runs scored.

Like this:

**RD = Runs Scored – Runs Allowed**

## What Is A Good Run Differential (RD) In Baseball?

How good the differential of a certain team is, mostly depends on the level of competition.

The more teams are evenly-matched in a league, the more difficult it will be to score high RD over the season.

**In MLB, a Run Differential of over +200 is usually the sign that the team belongs at the very top of the league and is a likely contender.**

**The best run differential ever in the MLB belongs to the New York Yankees, who had an RD of +411. **

**The worst RD ever is -723, achieved by Cleveland Spiders in 1889. **

Obviously, tougher competition nowadays means that those extreme values of RD are not possible anymore.

In 2021, the best Run Differential belonged to the LA Dodgers, who had +278. The Baltimore Orioles were the worst in the same season with -297.

## What Does RS Mean In Baseball?

**RS or Run Support is a stat measuring how many runs does the offense of a team scores while a certain pitcher (commonly a starter) of that team is in the game. **

This is the stat that the pitcher has no control of.

While he contributes to preventing the opposing team from scoring runs, he plays no role in how many runs his own team scores.

However, it does put his win/loss record into context.

With the help of RS, we can estimate whether the pitcher’s win percentage is too high or too low given the overall performance of a team and the rest of his stats.

It’s not too rare to see a pitcher with an excellent win percentage ranking relatively low in Run Support or vice versa.

High Run Support can make a pitcher look like a big winner even though his other stats are not so good.

## How To Calculate RS?

Run Support can be calculated in two ways.

**Commonly, RS is measured by taking the number of runs offense scores while a pitcher is in the game and then that number is set over 9 innings. **

This is why this stat is often referred to as RS/9. The other way is by simply using the number of runs per start.

Just like other pitching stats, like RA and ERA, Run Support can be adjusted for ballpark effects.

## Conclusion

An essential part of being a baseball fan is getting familiar with the statistics, at least to the basic point of understanding.

Stats and numbers are deeply rooted in baseball tradition and are getting even more important in modern times.

For almost any play that happens on the field, there’s a stat that takes note of what happened.

While no stat is perfect, they still help us understand the game better and have a better idea of how our team or favorite player performs.

When you understand them properly, stats like RA, RD, or RS give another dimension to baseball fandom and significantly enhance the game experience.