Kelvin Herrera, a right-handed pitcher from the Dominican Republic, became a familiar name in Major League Baseball during the 2010s. Born on December 31, 1989, in Tenares, Dominican Republic, Herrera's journey to the major leagues began when he signed with the Kansas City Royals as an amateur free agent in 2006. His early years in the minor leagues were marked by his impressive fastball, which consistently reached the upper 90s, and his ability to strike out batters with ease.

Herrera made his MLB debut with the Kansas City Royals on September 21, 2011. Over the next few years, he established himself as a reliable reliever in the Royals' bullpen. His breakout season came in 2012 when he appeared in 76 games, posting a 2.35 ERA and striking out 77 batters over 84.1 innings. His performance earned him a spot on the Royals' roster for the following seasons, where he continued to excel as a setup man.

The 2014 season was a turning point for Herrera and the Royals. He played a crucial role in the team's bullpen, which was often referred to as the "HDH" trio, consisting of Herrera, Wade Davis, and Greg Holland. This trio was instrumental in the Royals' run to the World Series that year. Herrera's ability to pitch in high-pressure situations was evident as he maintained a 1.41 ERA over 70 regular-season appearances. In the postseason, he continued to deliver, helping the Royals reach the World Series for the first time since 1985, although they ultimately fell to the San Francisco Giants in seven games.

The following year, in 2015, Herrera and the Royals returned with a vengeance. Once again, he was a key component of the bullpen, appearing in 72 games with a 2.71 ERA. The Royals dominated the postseason, and Herrera's contributions were vital in securing the team's first World Series championship in 30 years. His performance in the playoffs, particularly in the World Series against the New York Mets, solidified his reputation as a dependable reliever.

Herrera continued to be a mainstay in the Royals' bullpen through the 2016 and 2017 seasons. In 2016, he was selected for the MLB All-Star Game, a testament to his consistent performance and reliability on the mound. That year, he took on the role of closer for part of the season, recording 12 saves and maintaining a 2.75 ERA.

In 2018, the Royals traded Herrera to the Washington Nationals in June. Despite the change of scenery, he continued to perform well, though his season was cut short due to a foot injury. He became a free agent at the end of the season and signed with the Chicago White Sox in January 2019. His time with the White Sox was challenging, as he struggled to find the same level of success he had experienced earlier in his career. He was released by the White Sox in July 2020.

Throughout his career, Kelvin Herrera was known for his powerful fastball and his ability to handle high-pressure situations.