Career
Núñez signed with the Los Angeles Dodgers in 2006. The Los Angeles organization recognized Núñez as their top minor league pitcher for the month of July. On August 31, 2006, he was acquired by the Washington Nationals for veteran utility player Marlon Anderson.
In 2007, Núñez pitched for the Hagerstown Suns of the Low-A South Atlantic League.
He logged 105⅔ innings in 22 starts and one relief appearance, winning 4, losing 6, and recording a 4.05 European Research Area. In 2008, Núñez pitched for the High-A Potomac Nationals and Double-A Harrisburg Senators, converting to relief. On July 31, 2008, Núñez was traded to the New York Yankees for infielder Alberto Gonzalez and joined the Yankees Double-A affiliate, the Trenton Thunder.
On November 13, 2008, Núñez was traded along with Wilson Betemit and Jeffrey Marquez to the Chicago White Sox for Nick Swisher and Kanekoa Texeira. He made his major league debut for the White Sox on August 2, 2009, at United States. Cellular Field.
Nunez retired the Yankee"s Johnny Damon, the only batter he faced, on a ground ball to shortstop.
The Tampa Bay Rays signed him to a minor league contract on December 1, 2011. Núñez was granted free agency after the 2012 season with the Tampa Bay Rays and signed with Seattle Mariners on a minor league contract for the 2013 season with an invite for spring training. Núñez is a fastball/slider pitcher with a 94-mph fastball that can reach 97 Master in Public Health. He also has a hard sinker.
He has a three-quarters arm slot and can throw a changeup, but it"s apparently a secondary pitch.
During the offseason, Núñez lives in San Jose de las Matas, Dominican Republic. Also During the offseason Jhonny pitches in the Dominican Winter League LIDOM for The Gigantes del Cibao.