He played in Major League Baseball (MLB) from 1995 to 2001 for the Oakland Athletics and Tampa Bay Devil Rays.

Concerned that he would be unable to leave Cuba if he was highly valued as an athlete, Prieto intentionally pitched poorly during the winter of 1994.

Prieto, being unfamiliar with American banks and credit cards, walked around with his $1.2 million signing-bonus check in his pocket for over a week.

[5] On November 10, 2011, Prieto was announced as the pitching coach for the Vermont Lake Monsters, the Athletics' New York–Penn League (Single A, short season) team.

[6] From 2012 to 2015, Prieto served as interpreter for fellow Cuban defector, New York Mets outfielder Yoenis Céspedes.