He played in Major League Baseball (MLB) for the Cincinnati Reds, Milwaukee Brewers and New York Mets.

He was one of the smallest pitchers in recent Major League Baseball history at 5' 6", and one of the few to throw a true screwball.

[3][1] On December 21, 2007, Herrera was traded by the Rangers along with Edinson Vólquez to the Cincinnati Reds for Josh Hamilton.

[4] Two days after his debut, he was optioned back to AAA Louisville to make room on the roster for starting pitcher Homer Bailey.

He was briefly recalled again on June 10, 2008; however, he was sent down just four days later when pitcher Gary Majewski returned from the bereavement list.

He recorded his first victory of his career on June 16, 2009, after relieving Aaron Harang in the top of the third inning following an extended rain delay.