Kelvin de Jesús Herrera Mercado (born December 31, 1989) is a Dominican former professional baseball pitcher.

He played in Major League Baseball (MLB) for the Kansas City Royals from 2011 to 2018, Washington Nationals in 2018, and Chicago White Sox in 2019 and 2020.

Along with set-up man Wade Davis and closer Greg Holland, Herrera was part of one of the most prolific late inning trios in all of baseball.

During a game against the Oakland Athletics on April 19, 2015, Herrera was ejected for throwing a pitch behind Brett Lawrie.

[11] On April 25, 2015, Herrera was suspended an additional two games for his role in a brawl against the Chicago White Sox.

[13] Herrera, with the absence of Greg Holland in the 2015 postseason, became the eighth inning set-up man for the Royals.

[14] On June 18, 2018, the Royals traded Herrera to the Washington Nationals in exchange for three minor-league players (third baseman Kelvin Gutiérrez, outfielder Blake Perkins, and right-handed pitcher Yohanse Morel).

After he posted a combined 2.44 ERA for the Royals and the Nationals the previous season, the White Sox and Herrera agreed to a two-year deal on January 8, 2019.

On July 31, 2020, Herrera was designated for assignment in order to make room for Nick Madrigal on the 40-man roster.

[22][23] With an overhand delivery and quick explosion from the stretch, Herrera throws hard like many Dominican pitchers; his two-seam fastball averages about 97 mph and tops out at 103.