ERA is useful. It is also incomplete.
A team can post an excellent ERA because its pitchers dominate hitters, limit hard contact, avoid walks, and miss bats. But a good ERA can also reflect defense, sequencing, favorable outcomes with runners on base, or simply a stretch in which balls have found gloves instead of grass.
The reverse can happen too. A pitching staff can do many of the things we associate with good pitching and still carry an ERA that makes it look merely average.
That distinction becomes particularly interesting when we look across all 30 major-league teams in 2026.
Using FanGraphs team pitching data through September 4, I wanted to answer a slightly different question from the usual one. Instead of asking which teams have allowed the fewest earned runs, I asked:
Which teams appear to be pitching the best underneath those results?
That question leads us to Philadelphia.
But it also leads us to Milwaukee, Cleveland, Atlanta, Arizona, the Yankees, and several teams whose records do not line up neatly with the quality of their pitching.
Measuring the Pitching Process
No single pitching statistic completely describes a staff.
ERA tells us what happened. FIP focuses heavily on strikeouts, walks, hit batters, and home runs. xFIP normalizes the home-run component. SIERA attempts to estimate run prevention while accounting for strikeouts, walks, and batted-ball tendencies. xERA uses Statcast information about the quality of contact allowed.
Then there is K-BB%, one of the cleanest measures of pitcher control.
A staff that strikes out many hitters while walking few is usually doing something right.
I therefore built an Underlying Pitching Process Index using seven measures:
\mathcal{M} = \left\{ \mathrm{xERA}, \mathrm{FIP}^{-}, \mathrm{xFIP}^{-}, \mathrm{SIERA}, \mathrm{K\!-\!BB\%}, \mathrm{Barrel\%}, \mathrm{HardHit\%} \right\}The first step was to standardize every statistic across the 30 teams.
For team and pitching metric :
z_{i,m} = \frac{ x_{i,m} - \overline{x}_m }{ s_m }There is an important complication.
Higher K-BB% is good. Higher xERA is not. The same problem applies to FIP-, xFIP-, SIERA, Barrel%, and HardHit%.
I therefore adjusted the direction of each standardized statistic so that higher always means better pitching:
q_{i,m} = d_m z_{i,m}where:
d_m = \begin{cases} +1, & \mathrm{if\ higher\ values\ are\ better} \\ -1, & \mathrm{if\ lower\ values\ are\ better} \end{cases} q_{i,m} = d_m z_{i,m}where:
d_m = \begin{cases} +1, & \text{if higher values are better} \\ -1, & \text{if lower values are better} \end{cases}The seven adjusted z-scores were then averaged:
P_i = \frac{1}{7} \sum_{m \in \mathcal{M}} q_{i,m}Finally, I converted that score into an index centered on 100, with a standard deviation of 15:
I_i = 100 + 15 \left( \frac{ P_i - \overline{P} }{ s_P } \right)A score of 100 represents approximately league-average underlying pitching. A score of 115 is about one standard deviation above average.
This is important: the Process Index is not a FanGraphs statistic. It is a composite measure I constructed for this study from FanGraphs data.
And one team separates itself immediately.
Philadelphia Comes Out on Top
Figure 1 ranks all 30 teams using the Underlying Pitching Process Index.
Figure 1. 2026 MLB Team Pitching Through September 4: Underlying Pitching Process Ranking.
The index combines xERA, FIP-, xFIP-, SIERA, K-BB%, Barrel% allowed, and HardHit% allowed. The MLB average is centered at 100.
Philadelphia ranks first with a Process Index of 131.2.
Milwaukee is close behind at 128.6. The Yankees rank third, followed by Boston and the Dodgers.
The top ten are:
| Rank | Team | Process Index |
|---|---|---|
| 1 | Philadelphia | 131.2 |
| 2 | Milwaukee | 128.6 |
| 3 | New York Yankees | 121.6 |
| 4 | Boston | 118.6 |
| 5 | Los Angeles Dodgers | 117.4 |
| 6 | Toronto | 110.2 |
| 7 | Cleveland | 109.3 |
| 8 | New York Mets | 108.0 |
| 9 | Pittsburgh | 107.3 |
| 10 | Detroit | 107.3 |
Philadelphia’s position may initially seem strange.
The Phillies have a 4.00 ERA. Nobody looking only at ERA would identify that as the performance of baseball’s best pitching staff.
The underlying numbers tell a different story.
Philadelphia has a 3.56 xERA, 3.76 FIP, 3.54 xFIP, and 3.50 SIERA. Most impressively, the Phillies have a 17.9% K-BB%, the best figure in baseball through September 4.
That combination is difficult to dismiss.
They miss bats. They limit walks. Their contact profile is excellent. Several statistics designed specifically to isolate pitcher performance show a staff substantially better than its 4.00 ERA.
Milwaukee presents a different case.
The Brewers rank second in underlying process, with an index of 128.6, but their actual ERA is already excellent at 3.50. Their xERA is 3.47.
For Milwaukee, there is very little disagreement between process and outcome.
That distinction becomes important.
ERA and xERA Do Not Always Tell the Same Story
One simple way to measure the difference between observed and expected run prevention is:
\Delta \mathrm{ERA}_i = \mathrm{ERA}_i - \mathrm{xERA}_iA positive value means the team’s ERA has been worse than its xERA. A negative value means the team has allowed fewer earned runs than its expected ERA would suggest.
Figure 2 shows the relationship directly.
Figure 2. 2026 Team ERA vs. xERA Through September 4.
Teams below the diagonal have an ERA lower than their xERA. Teams above the diagonal have an ERA higher than expected from their Statcast contact profile.
Philadelphia stands out.
For the Phillies:
\Delta \mathrm{ERA}_{\mathrm{PHI}} = 4.00 - 3.56 = 0.44Their ERA is approximately 0.44 runs higher than their xERA.
That is a meaningful gap over nearly an entire season.
The Athletics are the extreme example of the opposite kind of outcome. Their ERA is 5.47, while their xERA is 4.48:
\Delta \mathrm{ERA}_{\mathrm{ATH}} = 5.47 - 4.48 = 0.99Oakland’s underlying pitching is not good. The Athletics rank only 24th in the Process Index.
But a 5.47 ERA makes the staff appear even worse than its underlying performance suggests.
Now look below the diagonal.
Arizona has a 4.17 ERA against a 4.72 xERA:
\Delta \mathrm{ERA}_{\mathrm{ARI}} = 4.17 - 4.72 = -0.55Atlanta is similar:
\Delta \mathrm{ERA}_{\mathrm{ATL}} = 3.57 - 4.04 = -0.47The Cubs sit at 4.16 versus a 4.62 xERA, while the Yankees have produced an exceptional 3.23 ERA despite a 3.67 xERA.
Those differences do not mean that one statistic is right and the other is wrong.
They tell us that something interesting is happening between underlying pitcher performance and actual runs allowed.
Process Is Not the Same as Results
To examine that distinction more directly, I created a second index.
The Results Index uses ERA-, RA9-WAR, and WPA. Unlike the Process Index, these measures deliberately capture more of what actually happened on the field.
The underlying results score is:
R_i = \frac{1}{3} \left( -z_{i,\mathrm{ERA}^{-}} + z_{i,\mathrm{RA9\!-\!WAR}} + z_{i,\mathrm{WPA}} \right)It is then converted to the same 100-centered scale:
J_i = 100 + 15 \left( \frac{ R_i - \overline{R} }{ s_R } \right)Figure 3 compares the two indices.
Figure 3. 2026 Team Pitching: Underlying Process vs. Actual Results.
Teams above the diagonal have obtained better results than their underlying pitching process would predict. Teams below the diagonal have performed worse.
The diagonal is the key.
Teams close to it have received results consistent with the quality of their underlying pitching. Teams far above or below it deserve more attention.
Philadelphia ranks first in process but only eighth in results.
Its Results Index is almost 20 points below its Process Index.
Arizona goes the other way. The Diamondbacks rank only 25th in underlying process, but 11th in results.
Atlanta is another striking example. The Braves rank 12th in process but second in results.
The Cubs rank 26th in process and 17th in results.
These teams have converted their pitching performances into actual run prevention more effectively than the underlying indicators alone would predict.
Philadelphia has not.
Neither have the Athletics, the Seattle Mariners, the San Francisco Giants, or the Mets.
There are many possible reasons. Defense is a factor. So does sequencing. Relievers inherit runners. Pitchers behave differently with runners on base. Ballparks are important as is random variation.
The point is not that all deviation must eventually disappear.
It is that ERA alone completely hides the deviation.
Strikeouts, Walks, and SIERA
One of the strongest relationships in the data appears when we compare K-BB% with SIERA.
Figure 4. 2026 Team Command and Dominance Through September 4.
Teams toward the right strike out more hitters relative to walks. Teams toward the top have lower SIERA.
K-BB% is appealing because it strips pitching down to two outcomes over which the pitcher exercises considerable control.
The calculation is simple:
\mathrm{K\!-\!BB\%} = \mathrm{K\%} - \mathrm{BB\%}Philadelphia again occupies elite territory.
The Phillies lead MLB at 17.9%. Milwaukee follows at 17.3%. The Dodgers are at 16.5%, with the Yankees and Cleveland both around 16%.
This is one reason Cleveland deserves more attention.
The Guardians are not surviving through a suspiciously low ERA or an unusually favorable gap between ERA and expected statistics. They rank fifth in SIERA and fifth in K-BB%.
That is a much stronger foundation.
Cleveland’s Pitching Is Not the Problem
Cleveland entered September 5 with a 72-70 record.
The Guardians’ pitching numbers, however, look like those of a considerably better team.
Cleveland ranks seventh in ERA, eighth in xERA, sixth in FIP, sixth in xFIP, fifth in SIERA, fifth in K-BB%, seventh in pitching WAR, seventh in the Underlying Pitching Process Index, and seventh in the Results Index.
That consistency is important.
Cleveland is not seventh because one unusual statistic dragged the composite upward. Almost every important run-prevention and defense-independent measure puts the Guardians somewhere in the same general neighborhood.
Their ERA is 3.75.
Their xERA is 3.90.
Their FIP is 3.86, xFIP is 3.88, and SIERA is 3.75.
There is, however, one weakness.
Cleveland ranks only around 21st in Barrel% allowed and 22nd in HardHit% allowed. Opponents have made better contact against the Guardians than the overall pitching rankings might imply.
They have compensated for that weakness largely through strikeouts and control.
That creates a somewhat unusual pitching profile. Cleveland is not especially dominant at suppressing every kind of hard contact. Still, the Guardians prevent enough balls from being put into play in the first place and avoid giving away enough free bases to remain an excellent overall staff.
If the question is why Cleveland has been only a little above .500, the team’s pitching data strongly suggests looking elsewhere.
How Much Does Pitching Explain Winning?
Of course, a baseball team does not win with pitching alone.
To measure the association between underlying pitching quality and the standings, I compared the Process Index with team winning percentage.
Winning percentage is:
\mathrm{WinPct}_i = \frac{ W_i }{ W_i + L_i }I then estimated a simple linear regression:
\mathrm{WinPct}_i = \alpha + \beta I_i + \varepsilon_iThe resulting relationship appears in Figure 5.
Figure 5. 2026 Underlying Pitching Quality vs. Team Winning Percentage.
The regression compares each team’s Process Index with its winning percentage through September 4.
The coefficient of determination is:
R^2 = 0.314Approximately 31.4% of the cross-team variation in winning percentage is associated with variation in the Underlying Pitching Process Index in this 2026 snapshot.
Pitching clearly is essential, but nearly 69% of the variation remains elsewhere.
The Cubs are 80-62 despite ranking 26th in underlying pitching process. Atlanta is 84-57 while ranking only 12th. Cleveland is 72-70 despite ranking seventh.
A team can compensate for mediocre pitching.
It can also waste very good pitching.
Philadelphia May Be Better Than Its ERA
The Phillies may be the most important example in the entire study.
Their 4.00 ERA does not look dominant. If we stopped there, we would never consider Philadelphia the best pitching team in baseball.
Yet the deeper indicators repeatedly return to the same conclusion.
Philadelphia ranks first in the Process Index. The Phillies lead baseball in K-BB%. Their xERA is 3.56. Their xFIP is 3.54. Their SIERA is 3.50.
Their actual ERA is the outlier.
That does not guarantee that the ERA will suddenly collapse toward 3.50. Baseball statistics do not work like a mechanical spring that must snap back to equilibrium.
But if I were trying to determine which pitching staff I trusted going forward, I would place more weight on the cluster of underlying measures than on ERA alone.
Philadelphia’s process has been elite.
Milwaukee Has the Cleaner Case
Milwaukee requires less explanation.
The Brewers rank second in the Process Index at 128.6 and have a 3.50 ERA against a 3.47 xERA.
There is almost no gap.
Their process says they are excellent. Their results say they are excellent. Their 88-54 record agrees.
Sometimes the complicated analysis confirms the obvious.
That is useful too.
Milwaukee does not need a regression argument or a discussion of sequencing to explain its success. The Brewers have simply pitched extremely well.
The Yankees Have Turned Good Pitching Into Great Results
The Yankees provide another variation.
New York ranks third in underlying process but first in the Results Index.
Their 3.23 ERA is substantially better than their 3.67 xERA:
\Delta \mathrm{ERA}_{\mathrm{NYY}} = 3.23 - 3.67 = -0.44The underlying staff is genuinely good. This is not a weak pitching team disguising itself behind a low ERA.
But the results have been even better than the already strong process.
That distinction is noteworthy.
The Yankees do not appear to be a mirage. They appear to be an excellent pitching staff that has also benefited from a gap between underlying performance and runs actually allowed.
Arizona Is More Difficult to Trust
Arizona presents a much different problem.
The Diamondbacks’ 4.17 ERA is not particularly impressive on its own, but it looks much better compared to their 4.72 xERA.
Their Process Index ranks only 25th in baseball.
Their Results Index ranks 11th.
That is one of the largest process-to-results gaps in the league.
Perhaps Arizona can continue converting that underlying performance into acceptable run prevention. There may be legitimate reasons for part of the difference.
Still, if the goal is prediction rather than description, I would be considerably more cautious about Arizona than Philadelphia.
The Phillies have poor results relative to a strong process.
Arizona has strong results relative to a poor process.
Those are not equivalent situations.
Oakland Shows How Ugly Results Can Become
At the bottom end, Oakland offers an equally useful lesson.
The Athletics rank 24th in underlying pitching process. That is bad, but not the worst in baseball.
Their Results Index ranks 30th.
Their 5.47 ERA is almost one full run higher than their 4.48 xERA.
The underlying numbers therefore suggest two conclusions at once.
Oakland has not pitched well.
Oakland has also gotten even worse results than its mediocre pitching would normally lead us to expect.
Both statements can be true.
What the Rankings Really Tell Us
This study is not intended to replace ERA with another single magic number.
In fact, that would defeat the purpose.
The more interesting lesson is that pitching has several layers.
There is the process: missing bats, limiting walks, controlling contact, suppressing barrels, and producing outcomes that FIP, xFIP, SIERA, and xERA consider sustainable.
Then there are the results.
Usually they move together.
Sometimes they do not.
Philadelphia has arguably produced the strongest underlying pitching process in baseball, yet received only the eighth-best composite results.
Milwaukee has been excellent by both standards.
The Yankees have turned excellent underlying pitching into even better results. Atlanta and Arizona have substantially outperformed what their process metrics would lead us to expect.
And Cleveland?
Cleveland may be the most revealing team of all.
The Guardians are barely above .500, yet almost every pitching measure says the staff belongs among the top quarter of baseball. Their Process Index ranks seventh. Their Results Index also ranks seventh.
There is little evidence that Cleveland’s pitching has betrayed the team.
If anything, it has kept the Guardians afloat.
Final Thoughts
ERA remains one of baseball’s most intuitive statistics because it measures something real. Runs crossed the plate, and those runs counted.
But describing what happened is not always the same as understanding why it happened.
That is where the deeper statistics become valuable.
Through September 4, Philadelphia appears to have baseball’s strongest underlying team pitching process. Milwaukee is close behind and has translated that process into superior run prevention. The Yankees have done even better in converting strong pitching into actual results.
Cleveland quietly belongs in the next group.
Meanwhile, Atlanta, Arizona, and the Cubs remind us that actual run prevention can exceed expectations based on underlying statistics, sometimes by a considerable margin.
None of those observations requires us to choose between ERA and advanced metrics.
We can use both.
ERA tells us what the scoreboard recorded.
The underlying statistics help us understand how the pitchers got there and perhaps where they are going next.
That difference is where the interesting part begins.
