Adjusted ERA+

Adjusted ERA+, often simply abbreviated to ERA+, is a statistic in baseball. It adjusts a pitcher's ERA according to the pitcher's ballpark (does it favor batters or pitchers) and the ERA of the pitcher's league. Average is set to be 100; a score above 100 indicates 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. However, if the average ERA in the league is 3.00, and the pitcher is pitching in a ballpark favoring pitchers, and the pitcher's ERA is 3.50, then the pitcher's ERA+ will be (significantly) below 100.

As a result, ERA+ is a good way of comparing pitchers' performances across different run environments. In the above example, the first pitcher has performed better than the second pitcher, but his ERA is higher. ERA+ corrects 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 4.91, which gave Martinez an ERA+ of 285. While Bob Gibson has the lowest ERA in modern times (1.12 in the 1968 National League) the average ERA was 2.99 that year (the so-called Year of the Pitcher) and so Gibson's ERA+ is 258, still highly impressive, but only sixth since 1900.

The career record for ERA+ (with a minimum of 1,000 innings pitched) is held by closer Mariano Rivera, who has a career ERA+ of 199. The career record ERA+ amongst retired players is 148, held by Lefty Grove. Walter Johnson, Dan Quisenberry, Hoyt Wilhelm and Smokey Joe Wood are tied in third place with a career ERA+ of 146.

Leaders

{|class="wikitable" style="font-size:98%;"
+Single Season Leaders!Rank !!Player !!Adjusted ERA+ !!Year !!Team
-!1
Tim Keefe ||align="center"|294 ||1880 ||Troy Trojans
-!2
Pedro Martínez ||align="center"|285 ||2000 ||Boston Red Sox
-!3
Dutch Leonard ||align="center"|279 ||1914 ||Boston Red Sox
-!4
Greg Maddux ||align="center"|273 ||1994 ||Atlanta Braves
-!rowspan=2|5
Walter Johnson ||align="center" rowspan=2|259 ||1913 ||Washington Senators
-
Greg Maddux ||1995 ||Atlanta Braves
-!7
Bob Gibson ||align="center"|258 ||1968 ||St. Louis Cardinals
-!8
Mordecai Brown ||align="center"|253 ||1906 ||Chicago Cubs
-!9
Pedro Martínez ||align="center"|245 ||1999 ||Boston Red Sox
-!10
Walter Johnson ||align="center"|240 ||1912 ||Washington Senators
-!11
Christy Mathewson ||align="center"|230 ||1905 ||New York Giants
-!rowspan=2| 12
Roger Clemens ||align="center" rowspan=2|226 ||1997 ||Toronto Blue Jays
-
Dwight Gooden ||1985 ||New York Mets
-!14
Grover Cleveland Alexander ||align="center"|225 ||1915 ||Philadelphia Phillies
-!15
Christy Mathewson ||align="center"|222 ||1909 ||New York Giants
-!rowspan=2| 16
Roger Clemens ||align="center" rowspan=2|221 ||2005 ||Houston Astros
-
Pedro Martínez ||1997 ||Montreal Expos
-!18
Lefty Grove ||align="center"|219 ||1931 ||Philadelphia Athletics
-!rowspan=2| 19
Jack Pfiester ||align="center"|216 ||1907 ||Chicago Cubs
-
Cy Young ||align="center"|216 ||1901 ||Boston Americans
-