Adjusted ERA+

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.^[1] 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.^[2]

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.^[3] 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.

Leaders

Players in bold are active as of the end of the 2014 season and have not announced their retirement.

Single-season leaders include only pitchers eligible for the ERA title (a pitcher must throw a minimum of one inning per game scheduled for his team during the season to qualify for the ERA title).^[4] Only pitchers with 1500 or more innings pitched are shown in the career leader list.

Career Leaders Rank Player Adjusted ERA+ 1 Pedro Martínez 154 2 Clayton Kershaw 151 3 Lefty Grove 148 4 Walter Johnson 147 5 Ed Walsh 145 6 Roger Clemens 143 7 Addie Joss 142 8 Kid Nichols 140 9 Mordecai Brown 139 10 Cy Young 138 11 Johan Santana 136 T-12 Pete Alexander 135 Christy Mathewson Randy Johnson Rube Waddell T-16 Whitey Ford 133 John Clarkson Adam Wainwright Harry Brecheen T-20 Greg Maddux 132 Al Spalding Félix Hernández Noodles Hahn T-24 Sandy Koufax 131 Dizzy Dean Roy Halladay T-27 Carl Hubbell 130 Hal Newhouser 29 Amos Rusie 129

Single Season Leaders Rank Player Adjusted ERA+ Year Team 1 Tim Keefe 293 1880 Troy Trojans 2 Pedro Martínez 291 2000 Boston Red Sox 3 Dutch Leonard 282 1914 Boston Red Sox 4 Greg Maddux 271 1994 Atlanta Braves 5 Greg Maddux 260 1995 Atlanta Braves 6 Walter Johnson 259 1913 Washington Senators 7 Bob Gibson 258 1968 St. Louis Cardinals 8 Mordecai Brown 253 1906 Chicago Cubs 9 Pedro Martínez 243 1999 Boston Red Sox 10 Walter Johnson 240 1912 Washington Senators 11 Christy Mathewson 230 1905 New York Giants 12 Dwight Gooden 229 1985 New York Mets 13 Roger Clemens 226 2005 Houston Astros 14 Pete Alexander 225 1915 Philadelphia Phillies T-15 Christy Mathewson 222 1909 New York Giants Roger Clemens 1997 Toronto Blue Jays T-17 Cy Young 219 1901 Boston Americans Pedro Martínez 1997 Montreal Expos 19 Denny Driscoll 218 1882 Pittsburgh Alleghenys 20 Lefty Grove 217 1931 Philadelphia Athletics

References

1. 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.
2. Baseball Trivia (General) - Pitchers mound, allexperts.com.
3. 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.
4. "Official Rules: 10.00 The Official Scorer". Major League Baseball. Retrieved June 2015.