Comparison Shopping Part 1: ERA+

Bob Gibson took advantage of higher mounds (plus his already formidable skill) to post a modern-era record 1.12 ERA in 1968. But how does that compare to other incredible pitching performances? (Courtesy of Focus on Sports/Getty Images)

If I were to argue with you about why Tim Raines should be in the Hall of Fame, I could point to a lot of stats, but this tweet from Twitter stathead Ryan Spaeder (@theaceofspaeder) comparing his numbers to first-ballot Hall of Famer Tony Gwynn makes (some) of my point.

Without statistics, most of us probably wouldn’t even know who Tim Raines is. But thanks to the Sabermetrics boom and a new appreciation for getting on base, Raines has received a surge in Hall of Fame voting, making it a decent possibility he gets in in his final year of eligibility. (I love Raines more than a lot of things, by the way. I will go to bat – damn that’s a bad pun – for him any day.)

Statistics provide us with a point of comparison beyond things like Gold Gloves and MVPs. They give us proof – or disprove – for what we see with our eyes, and allow us to compare players in a multitude of ways.

But how do you compare players from different eras? For example: obviously Bob Gibson had some of the best numbers of all-time – good enough to force Major League Baseball to lower the mounds – but weren’t numbers better across the board? How does he stack up against other historically great seasons?

(Yes, I’m aware I opened this up talking about a hitter but now I’m transitioning into talking pitchers. I told you, I’m all about Tim Raines and will shoehorn him into anything.)

Luckily, people much smarter than I were on the case and created ERA+, which is overall incredibly simple but provides a valuable tool to compare players across eras (ERA and era are going to get very confused in here, just you wait).

ERA+ is simply the league average ERA divided by the player’s ERA, and then multiplied by 100. It also factors in whether the pitcher pitches in a hitter-friendly or pitcher-friendly park. While I’ve gone over why Earned Run Average is a flawed statistic, for simple comparison it serves its purpose.

By dividing the league average ERA by the player’s, the numbers are adjusted to have a better sense of how good the numbers are in context of the year. When this number is multiplied by 100, it puts them on an easily-discernable scale: 100 is league average, above is above average, and below is below average.

So let’s look at Bob Gibson’s dominant 1968 season that resulted in the lowering of the mounds in 1969.

Year W L ERA GS CG SHO IP H ER HR BB SO FIP WHIP H9 BB9 SO9
1968 ★ 22 9 1.12 34 28 13 304.2 198 38 11 62 268 1.77 0.853 5.8 1.8 7.9
Provided by Baseball-Reference.com: View Original Table
Generated 6/21/2016.

Gibson was beyond dominant in what was the best year for pitching post Dead-Ball Era. His ERA was the best by any pitcher not just in the majors that season, but also since the Dead-Ball Era (including that time, and pre-modern baseball, Gibson in 1968 had the 4th best ERA of all-time).

Gibson was well-known as a fierce competitor, and while he may be 80 years old now, I wouldn’t want him to know that I’m about to question the status of that incredible performance.

But how does that compare not just across eras, but also in relation to how good other pitchers were at the time? Well, his ERA+ was 258, which is 7th all time.

So what does that even mean?

It means that while incredibly impressive, Gibson’s ERA was affected immensely by the league, and 50 players had ERAs of 3.00 or lower (and seven had sub-2.00 ERAs). Gibson’s 1.12 ERA is the best of a more modern era of baseball, but it was less (admittedly only slightly so) impressive then than it would be now.

So who had the best ERA+? Well that would be Tim Keefe, who pitched to a 293 ERA+ in his first season with the Troy Trojans in 1880 thanks to his 0.86 ERA (also a record). He actually only made 12 appearances and threw 105 innings, so he’s essentially a small sample-size fluke.

Discounting players who played when it took eight balls to walk a batter (Fun fact: 1880 was the year the National League – which would later become Major League Baseball in 1903 – changed the number of balls required from a walk from nine to eight.), the best ERA+ of all-time belongs to none other than Pedro Martinez for his unbelievable 2000 season with the Red Sox.

Year W L ERA GS CG SHO IP H ER HR BB SO ERA+ FIP WHIP H9 BB9 SO9
2000 ★ 18 6 1.74 29 7 4 217.0 128 42 17 32 284 291 2.17 0.737 5.3 1.3 11.8
Provided by Baseball-Reference.com: View Original Table
Generated 6/22/2016.

Incredibly, Pedro’s numbers in 2000 wouldn’t have been out-of-place in 1968, except for the number of complete games. Put that 1.74 ERA in context, and it comes out to an ERA+ of 291, just two points behind Tim Keefe and his small-sample size.

2000 was basically the worst year to be a pitcher. The league average ERA was 4.77. The only years with worse average ERAs were 1894 (5.33) and 1930 (4.81).

The main reason for this: it was right in the heart of the Steroid Era. The average slugging percentage of .437 is the highest in the history of not just Major League Baseball, but even stretching back to when there was just the National League. Tack on a .345 OBP, and the .782 OPS (on-base plus slugging percentage) is the third-worst of all time (directly correlating with the other two high ERAs).

So that’s why Pedro’s 1.742 ERA rates as the best ERA+ of the modern ERA, despite being the 107th lowest ERA in the history of baseball. He was the only pitcher who qualified for the ERA title in 2000 with a sub-2.50 ERA. Only five pitchers had an ERA at or below 3.00. More pitchers in 1968 had sub-2.00 ERAs.

(Another interesting side note about those other sub-2.00 pitchers in 2000: 3 of them – Kevin Brown, Randy Johnson and Greg Maddux – were all over the age of 33. The other pitcher, Jeff D’Amico of the Brewers, had a 6.08 ERA in 2001 and was out of baseball by 2005. He was 24 in 2000.)

ERA+ is one of the easiest ways to at-a-glance compare generational greatness as it puts everything into context and onto an easy scale. It provides an easily referenced point of comparison for your next argument about what pitcher really is the greatest of all-time (according to ERA+, Mariano Rivera with a 208) or whether Clayton Kershaw is really this good (he’s second all time with a 158, and the nearest active pitcher is Adam Wainwright at 129. And his current 2016 ERA+ is 245, which would be good for ninth).

Statistics, when used correctly, can serve as a strong backbone to any argument. ERA+ provides us with one we can use at any time across eras.

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