baseball statistics Baseball statistics play an important role in evaluating the progress of a player or team. Since the flow of a baseball game has natural breaks to it, and normally players act individually rather than performing in clusters, the sport lends itsel ...

, strikeouts per nine innings pitched (K/9, SO/9, or SO/9IP) is the

mean There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set. For a data set, the ''arithme ...

strikeouts In baseball or softball, a strikeout (or strike-out) occurs when a batter accumulates three strikes during a time at bat. It usually means that the batter is out. A strikeout is a statistic recorded for both pitchers and batters, and is deno ...

(or Ks) by a

pitcher In baseball, the pitcher is the player who throws ("pitches") the baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or draw ...

per nine

innings pitched In baseball, innings pitched (IP) are the number of innings a pitcher has completed, measured by the number of batters and baserunners that are put out while the pitcher is on the pitching mound in a game. Three outs made is equal to one innin ...

. It is determined by multiplying the number of strikeouts by nine, and dividing by the number of innings pitched. To qualify, a pitcher must have pitched 1,000 innings, which generally limits the list to starters. A separate list is maintained for

reliever In baseball and softball, a relief pitcher or reliever is a pitcher who enters the game after the starting pitcher is removed because of fatigue, ineffectiveness, injury, or ejection, or for other strategic reasons, such as inclement weather ...

s with 300 innings pitched or 200 appearances.

Leaders

The all-time leader in this statistic through 2021 was

Robbie Ray Robert Glenn Ray (born October 1, 1991) is an American professional baseball pitcher for the Seattle Mariners of Major League Baseball (MLB). He previously played for the Detroit Tigers, Arizona Diamondbacks, and Toronto Blue Jays. Ray was an M ...

(11.10). The only other pitchers who had averaged over 10 strikeouts were

Chris Sale Christopher Allen Sale (born March 30, 1989) is an American professional baseball pitcher for the Boston Red Sox of Major League Baseball (MLB). He previously played in MLB for the Chicago White Sox, with whom he made his major league debut ...

(11.08),

Yu Darvish , more commonly known as Yu Darvish (ダルビッシュ有), is a Japanese professional baseball pitcher for the San Diego Padres of Major League Baseball (MLB). Darvish has also played in MLB for the Texas Rangers, Los Angeles Dodgers, and ...

(11.04),

Jacob deGrom Jacob Anthony deGrom (born June 19, 1988), is an American professional baseball pitcher for the Texas Rangers of Major League Baseball (MLB). He has previously played in MLB for the New York Mets. Prior to playing professionally, deGrom attend ...

(10.88),

Max Scherzer Maxwell Martin Scherzer (born July 27, 1984) is an American professional baseball pitcher for the New York Mets of Major League Baseball (MLB). He previously played in MLB for the Arizona Diamondbacks, Detroit Tigers, Washington Nationals, and L ...

(10.73),

Randy Johnson Randall David Johnson (born September 10, 1963), nicknamed "The Big Unit", is an American photographer and former professional baseball pitcher who played 22 seasons in Major League Baseball (1988–2009) for six teams, primarily the Seattle M ...

(10.61),

Stephen Strasburg Stephen James Strasburg (; born July 20, 1988) is an American professional baseball pitcher for the Washington Nationals of Major League Baseball (MLB). Strasburg was selected by Washington with the first overall pick in the 2009 Major League ...

(10.55),

Gerrit Cole Gerrit Alan Cole (born September 8, 1990) is an American professional baseball pitcher for the New York Yankees of Major League Baseball (MLB). He previously played for the Pittsburgh Pirates and Houston Astros. Cole played for the baseball team ...

(10.39),

Kerry Wood Kerry Lee Wood (born June 16, 1977) is an American former baseball pitcher who played 14 seasons in Major League Baseball (MLB) for the Chicago Cubs, Cleveland Indians, and New York Yankees. Wood first came to prominence as a 20-year-old rooki ...

(10.32), Aaron Nola (10.08), and

Pedro Martinez Pedro is a masculine given name. Pedro is the Spanish, Portuguese, and Galician name for '' Peter''. Its French equivalent is Pierre while its English and Germanic form is Peter. The counterpart patronymic surname of the name Pedro, meaning ...

(10.04). The top three in 2022 were

Carlos Rodon Carlos may refer to: Places ;Canada * Carlos, Alberta, a locality ;United States * Carlos, Indiana, an unincorporated community * Carlos, Maryland, a place in Allegany County * Carlos, Minnesota, a small city * Carlos, West Virginia ;Elsewher ...

(11.98),

Shohei Ohtani , nicknamed "Shotime", is a Japanese professional baseball pitcher, designated hitter and outfielder for the Los Angeles Angels of Major League Baseball (MLB). He previously played for the Hokkaido Nippon-Ham Fighters of Nippon Professional B ...

(11.87), and

(11.53). Among qualifying relievers,

Aroldis Chapman Albertín Aroldis Chapman de la Cruz (; born February 28, 1988) is a Cuban-born American professional baseball relief pitcher who is a free agent. He has played in Major League Baseball (MLB) for the Cincinnati Reds, New York Yankees and C ...

(14.88) was the all-time leader in strikeouts per nine innings through 2020, followed by

Craig Kimbrel Craig Michael Kimbrel (born May 28, 1988) is an American professional baseball pitcher for the Philadelphia Phillies of Major League Baseball (MLB). He has previously played in MLB for the San Diego Padres, Boston Red Sox, Atlanta Braves, Chicag ...

(14.66),

Kenley Jansen Kenley Geronimo Jansen (born September 30, 1987) is a Curaçaoan professional baseball pitcher for the Boston Red Sox of Major League Baseball (MLB). He has previously played in MLB for the Los Angeles Dodgers and Atlanta Braves. Signed by the ...

(13.25),

Rob Dibble Rob or ROB may refer to: Places * Rob, Velike Lašče, a settlement in Slovenia * Roberts International Airport (IATA code ROB), in Monrovia, Liberia People * Rob (given name), a given name or nickname, e.g., for Robert(o), Robin/Robyn * Rob ...

(12.17), David Robertson (11.93), and

Billy Wagner William Edward Wagner (born July 25, 1971), nicknamed "Billy the Kid", is an American former professional baseball pitcher who played 16 seasons in Major League Baseball (MLB). He pitched for the Houston Astros (1995–2003), Philadelphia Phil ...

(11.92).

Analysis

One effect of K/9 is that it may reward or "inflate" the numbers for pitchers with high batting averages on balls in play (BABIP). Two pitchers may have the same K/9 rates despite striking out a different percentage of batters since one pitcher will pitch to more batters to obtain the same cumulative number of strikeouts. For example, a pitcher who strikes out one batter in an inning, but also gives up a

walk Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults ov ...

or a

hit Hit means to strike someone or something. Hit or HIT may also refer to: Arts, entertainment and media Fictional entities * Hit, a fictional character from '' Dragon Ball Super'' * Homicide International Trust, or HIT, a fictional organization ...

, strikes out a lower percentage of batters than a pitcher who strikes out one batter in an inning without allowing a baserunner, but both have the same K/9.

References

Pitching statistics {{Baseball-stub