Kenley Geronimo Jansen (born September 30, 1987) is a Curaçaoan professional baseball pitcher for the Los Angeles Dodgers of Major League Baseball.
Jansen was signed as an undrafted free agent catcher by the Dodgers in 2005 and was assigned to the Rookie Class Gulf Coast Dodgers, where he played in 2005 and 2006. He split 2007 between the Ogden Raptors and the Class-A Great Lakes Loons. In 2008 with the Loons, he hit .227 and 9 home runs in 79 games.
In 2009, he was the starting catcher for the Netherlands team in the World Baseball Classic. In the Netherlands' upset of the favored Dominican Republic team, Jansen threw out Willy Taveras on an attempted steal of third base in the ninth inning, a key play in the game.
With the Inland Empire 66ers of San Bernardino in 2009, the Dodgers began an attempt to convert Jansen from a catcher into a relief pitcher. After the season, he pitched in the Arizona Fall League and was added to the Dodgers 40 man roster. On May 15, 2010 he was promoted to the Double-A Chattanooga Lookouts, where he was selected to the mid-season Southern League all-star game.
On July 23, 2010, Jansen was promoted to the Dodgers. He made his Major League debut in relief on July 24 against the New York Mets, pitching a scoreless inning, retiring all three batters he faced, striking out two. The very next day on July 25, he recorded his first Major League save, when he pitched a 1-2-3 inning against the New York Mets.
On August 26, 2010, Jansen walked and scored a run in his first Major League plate appearance at Miller Park in Milwaukee against Yovani Gallardo. He collected his first Major League hit on August 31, 2010 at Dodger Stadium. The hit was a single up the middle against Kyle Kendrick of the Philadelphia Phillies. He recorded his first Major League win against the Houston Astros on September 11, 2010 in Minute Maid Park.
He appeared in 25 games with the Dodgers in 2010, working 27 innings with a 1–0 record and a 0.67 ERA. He also saved four games in 2010.
In 2011 Jansen became a key member of the Dodgers bullpen. He was 2–1 with a 2.85 ERA in 53 2⁄3 innings and saved 5 games. He also struck out 96 batters, setting a new Major League season record with 16 1⁄3 strikeouts per nine innings.
In May 2012, Jansen became the Dodgers closer after Javy Guerra struggled in the role. At the end of the season, after missing some time due to heart problems, Jansen was replaced as closer by Brandon League.
He appeared in 65 games with a 5–3 record, 2.35 ERA, 99 strikeouts and 25 saves.
Jansen was a late addition to the Netherlands national baseball team for the 2013 World Baseball Classic, as he was added to the roster for the semi-finals but did not appear in the game.
Jansen began 2013 as the setup man in the bullpen but resumed the role as closer when League struggled. He was in 75 games with a 4-3 record, 1.88 ERA and 28 saves.
On February 11, 2014 he avoided his first arbitration hearing by signing a $4.3 million contract with the Dodgers. Fully established as the Dodgers closer in 2014, Jansen worked in 68 games with a 2.76 ERA, 101 strikeouts and 44 saves. He became just the fourth Dodger pitcher in history with 40+ saves in a season, joining Éric Gagné (who did it three times), Todd Worrell and Jeff Shaw.
On January 16, 2015, he again avoided arbitration by signing a one-year $7.425 million contract with the Dodgers. However, on February 17, he underwent surgery to remove a growth from a bone in his left foot. The recovery time kept him out of action until May. Jansen was eventually activated off the disabled list on May 15 and rejoined the Dodgers roster. Jansen struck out 23 batters in his first 14 games of the season, without giving up a single walk. This broke Jay Howell's team records (set in the 1991 season) of 13 games without a walk to start a season and 20 strikeouts without a walk to start a season. He wound up striking out 27 before he finally walked a batter on June 30, eight shy of the major league record. He made 54 appearances for the team in 2015 with a 2.41 ERA and 36 saves. He also struck out 80 batters, while only walking 8 all season. He became the first Dodgers pitcher with five seasons of 80 or more strikeouts in relief. In his final year of arbitration, Jansen signed a one-year, $10.65 million, contract with the Dodgers on January 15, 2016.