In the minor leagues, Hernández showed poor patience and high strikeouts typical of a teenager[citation needed] and did not rise past single-A until 2004.

He returned later in the season and hit his first Major League home run on September 19, 2006, off Florida Marlins pitcher Scott Olsen.

On August 20, 2008, Hernández was dealt to the Washington Nationals as a player to be named later for relief pitcher Luis Ayala.

[2] On August 20, 2008, Hernández was dealt to the Washington Nationals as a player to be named later for relief pitcher Luis Ayala.

[3] Hernández was traded back to the New York Mets on August 6, 2009, in exchange for minor league infielder Greg Veloz.

Hernández had the opportunity to compete for the starting second baseman position, but lost to Jayson Nix; he was subsequently used in a utility infielder role.

On July 18, Hernández was designated for assignment to make room on the active roster for pitcher Jeanmar Gómez.

[citation needed] He and shortstop Erick Aybar are called "los menores" (Spanish for "the kids") and were known as one of the best middle infields in the Dominican Republic.

[10] On 29 October, 2016, it was confirmed that Hernandez would be released from the Dragons along with Ricardo Nanita, Juan Jaime, Drew Naylor and Leyson Septimo.