Adjusted ERA+, often simply abbreviated to ERA+ or ERA plus, is a pitching statistic in baseball. It adjusts a pitcher's earned run average (ERA) according to the pitcher's ballpark (in case the ballpark favors batters or pitchers) and the ERA of the pitcher's league. Average ERA+ is set to be 100; a score above 100 indicates that the pitcher performed better than average, below 100 indicates worse than average.
For instance, if the average ERA in the league is 4.00, and the pitcher is pitching in a ballpark that favors hitters, and his ERA is 4.00, then his ERA+ will be over 100. Likewise, if the pitcher is pitching in a ballpark favoring pitchers, then the pitcher's ERA+ will be below 100.
As a result, ERA+ can be used to compare pitchers across different run environments. In the above example, the first pitcher may have performed better than the second pitcher, even though his ERA is higher. ERA+ can be used to account for this misleading impression.
Pedro Martínez holds the modern record for highest ERA+ in a single season; he posted a 1.74 ERA in the 2000 American League, which had an average ERA of 4.92, which gave Martínez an ERA+ of 291. While Bob Gibson has the lowest ERA in modern times (1.12 in the National League in 1968), the average ERA was 2.99 that year (the so-called Year of the Pitcher) and so Gibson's ERA+ is 258, sixth highest since 1900. 1968 was the last year that Major League Baseball employed the use of a pitcher's mound greater than 10 inches.
The career record for ERA+ (with a minimum of 1,000 innings pitched) is held by Mariano Rivera, a closer whose career ERA+ is 205. Upon retirement in 2013, with an ERA+ of 194 in his final season, Rivera's career record of 205 surpassed the record among retired players of 154, held by Martínez, bumping Jim Devlin, a pitcher in the 1870s, to third with 151. Among qualifying pitchers, Pedro Martínez has the most separate seasons with an ERA+ over 200, with five, and the most consecutive 200 ERA+ seasons (4), though the closer Rivera, with too few innings each year to qualify officially, has surpassed 200 ERA+ in 13 seasons of his 19 seasons, including 4 consecutive seasons twice and 5 consecutive seasons once and also surpassing 300 in 2004 and again in 2008. Roger Clemens topped a 200 ERA+ three times, and Greg Maddux had two such seasons.
Players in bold are active as of the end of the 2014 season and have not announced their retirement. This list is horribly inaccurate and someone should probably go about editing it. Billy Wagner was previously omitted from the all time leaders, and Mariano Rivera's unprecedented single-season ERA+ of 308 in 2005 is omitted, just to name a few omissions / errors, unless there is a minimum innings limit which has not been specified anywhere
- Single season awards require a minimum of one inning pitched for each game played (thus usually 162 IP in today's game). Thus closers and other relievers will not generally acquire enough innings pitched to qualify.
- Baseball Trivia (General) - Pitchers mound, allexperts.com.
- Baseball Reference career ERA+ leaders, accessed October 21, 2013 (after the 2013 regular season, with Rivera having pitched his last game, had his number retired by the Yankees, but Baseball Reference not yet having marked him as retired on their site). Also the source for the corresponding table.