Earned Run Average is a Bad Statistic and Should be Retired
The most common number for pitchers — ERA — is also the most inaccurate.
Baseball has exploded with different measurements for player performance; wRC+, ERA-, DRA, FIP, xFIP, WAR, and more are commonplace in player evaluation discussions. But the most common statistic used to evaluate pitching is also the most rudimentary; ERA.
Earned Run Average is calculated as (ER/IP)*9; so earned runs allowed divided by innings pitched and multiplied by nine. It’s supposed to give a snapshot into how many earned runs a pitcher would give up on average if they threw nine innings. On the surface, it makes complete sense and is nice, simple, and very clear to the naked eye. There’s only one problem: there are inherent flaws with the formula.
Earned runs are the most arbitrary part of evaluating a pitcher’s performance because it doesn’t actually measure how well a pitcher performed. Earned runs also take into account the defense behind the pitcher which is completely out of their control. If a good pitcher has a bad defense behind him, some hits that an average defender would get to might squeak through and lead to more runs. How is that fair? Why should the pitcher be evaluated by the performance and the capabilities of the defense behind them? It’s unrealistic to assess a player’s performance based on the abilities of their supporting cast. It’s like saying Tom Hanks was only good in Forrest Gump because Robin Wright was a great Jenny or because Gary Sinise’s Lieutenant Dan made the performance.
There’s one slight problem with incorporating defense into a pitcher’s evaluation; we don’t have a good way to evaluate defense. Places like Fangraphs have attempted to measure a player’s defense using statistics like range factor, Ultimate Zone Rating, and Defensive Runs Saved, but it’s hard to take them seriously given the arbitrary history of defensive statistics. There’s still human error factoring into most of these numbers and, until that can be eliminated, the defensive stats will never be truly accurate. The best way to avoid the issue is to discount defensive performance entirely when evaluating a pitcher.
FIP, or Fielding Independent Pitching, attempts to do just that; measure a pitchers performance outside of the defense. FIP measures the “three true outcomes” for a pitcher — walks, strikeouts, and home runs — and outputs a number in the same format as ERA. This gives a better insight to what the pitcher does with what he can control and eliminates the ever-changing variable in the defense. There’s also xFIP, which is FIP adjusted for ballparks. Neither statistic is perfect, but it gives a much better insight into how well a pitcher is performing.
Two pitchers — Jon Gray and Adam Wainwright — have outperformed their ERA while three others — Kyle Hendricks, Madison Bumgarner and Marco Estrada — have seen success behind top defenses.
Gray, the Colorado Rockies rookie, has seen his ups and downs this year, but overall has performed well for Colorado’s standards. His ERA is 4.55 and his FIP/xFIP is 3.87/3.70 a difference of 0.75. Gray has put up some crooked numbers lately and has been pretty hittable, but it isn’t entirely his fault; in his last start, the Rockies defense committed three errors behind him.
As a whole, Colorado’s defense is ranked 16th by FanGraphs Defensive Runs Above Average (DEF) at -5.8 runs. The Rockies are in the middle of the pack, but are below average on defense statistically and it shows in their pitching statistics. They also deal with an extreme hitter’s park in Coors Field which can skew their numbers even more. Essentially, Gray is penalized for the below-average defense behind him despite keeping the strikeouts up and home runs down.
Wainwright suffers from a similar problem; a bad defense leads to more “earned” runs. Wainwright’s ERA of 4.72 is less than encouraging, but his FIP/xFIP sits at 3.49/4.05, a difference of 1.23 runs. Even his park-adjusted number is 0.67 runs better than his ERA, suggesting that Wainwright has outperformed his defense. The Cardinals, by the same DEF statistic, rank 27th at -28.6 runs. The Cardinals have lost nearly three games based solely on how bad their defense has been. Wainwright hasn’t been as good as he has been over the last few years, but he’s been much better than his 4.72 ERA would suggest.
Like all numbers, there are players benefiting from the inefficiencies. Kyle Hendricks has had an amazing and unexpected year so far, posting an ERA of 2.19, good for second in the majors. His FIP/xFIP is another story; a 3.38/3.62 suggests that he’s been good, but not as good as his ERA suggests. He’s had a lot of help; the Cubs are tops in the majors with 42.5 defensive runs above average, which equals about four to five wins.
Bumgarner and Estrada have also seen some benefits from a good defense. The Giants are third in the majors with a DEF of 35.9 while the Blue Jays are fifth with 29.2. Bumgarner’s ERA is a pretty 2.11 and Estrada’s 88 MPH fastball has led to a 2.95 ERA. Their FIP/xFIP’s tell a different story; Bumgarner’s 3.14/3.52 is still good but not great while Estrada’s 3.92/4.49 are worse than both Gray and Wainwright, who haven’t been good this year according to ERA. Bumgarner and Estrada have something that Gray and Wainwright don’t; a good defense.
Imagine walking into your yearly review and hearing this from your boss; Your performance was great, but your co-workers on your team couldn’t meet enough deadlines so we’re going to penalize you for that. Sucks. Is that fair? Should you be judged on your teammates performance? Should you not receive the bonus and recognition because your management team didn’t put a solid team around you or they didn’t live up to expectations?
No. And neither should pitchers.
