A groundball pitcher, sometimes referred to as "wormkillers" for the number of balls that hit the dirt and "kill worms" is a pitcher that relies on getting hitters to hit into ground outs instead of flyballs or strikeouts.

Most groundball pitchers rely heavily pitches with good downward movement (sink), such as the sinker

Sinker (baseball)

In baseball, a sinker , is a type of fastball pitch which has significant downward and horizontal movement. The sinker is known for inducing a lot of ground balls...

, the two-seam fastball

Two-seam fastball

A two-seam fastball is a pitch in baseball and a variant of the straight fastball. The pitch has the speed of a fastball, but the general movement of a screwball...

, and the splitter

Split-finger fastball

A split-finger fastball or splitter is a pitch in baseball. It is named after the technique of putting the index and middle finger on different sides of the ball, or "splitting" them. When thrown hard, it appears to be a fastball to the batter, but suddenly "drops off the table" towards home...

/forkball

Forkball

The forkball is a type of pitch in baseball. Related to the split-fingered fastball, the forkball is held between the first two fingers and thrown hard snapping the wrist....

. These pitches are used to 'jam' hitters, causing them to hit the ball into the ground, and to an infielder

Infielder

An infielder is a baseball player stationed at one of four defensive "infield" positions on the baseball field.-Standard arrangement of positions:In a game of baseball, two teams of nine players take turns playing offensive and defensive roles...

. As a result, many groundball pitchers have a very high groundout to flyout ratio

Ground ball fly ball ratio

In baseball statistics, ground ball fly ball ratio , also known as ground outs per fly outs/air outs , is a measure of:...

 (GO-AO), and a high number of double plays turned. Examples include Arizona Diamondbacks

Arizona Diamondbacks

The Arizona Diamondbacks are a professional baseball team based in Phoenix. They play in the West Division of Major League Baseball's National League. From 1998 to the present, they have played in Chase Field...

 pitcher Brandon Webb

Brandon Webb

Brandon Tyler Webb is a Major League Baseball pitcher. He was the 2006 National League Cy Young Award winner.-High school:Webb attended Paul G...

, Atlanta Braves

Atlanta Braves

The Atlanta Braves are a professional baseball club based in Atlanta, Georgia. The Braves are a member of the Eastern Division of Major League Baseball's National League. The Braves have played in Turner Field since 1997....

 pitcher Derek Lowe

Derek Lowe

Derek Christopher Lowe is a Major League Baseball starting pitcher for the Cleveland Indians. He throws and bats right-handed. He is 6'6" and 230 pounds.-Early years:...

, Colorado Rockies

Colorado Rockies

The Colorado Rockies are a Major League Baseball team based in Denver, Colorado. Established in 1991, they started play in 1993 and are in the West Division of the National League. The team is named after the Rocky Mountains...

 pitcher Aaron Cook, Minnesota Twins

Minnesota Twins

The Minnesota Twins are a professional baseball team based in Minneapolis, Minnesota. They play in the Central Division of Major League Baseball's American League. The team is named after the Twin Cities area of Minneapolis and St. Paul. They played in Metropolitan Stadium from 1961 to 1981 and the...

 pitcher Nick Blackburn and Washington Nationals

Washington Nationals

The Washington Nationals are a professional baseball team based in Washington, D.C. The Nationals are a member of the Eastern Division of the National League of Major League Baseball . The team moved into the newly built Nationals Park in 2008, after playing their first three seasons in RFK Stadium...

 pitcher Chien-Ming Wang

Chien-Ming Wang

Chien-Ming Wang is a Taiwanese Major League Baseball pitcher. He was initially signed as an amateur free agent by the New York Yankees for the 2000 season, and played for the Staten Island Yankees...

.