Career
Sierra played for Holguín and Sancti Spíritus in the Cuban National Series. In April 2015, Sierra defected from Cuba to the United States to pursue a Major League Baseball (MLB) career. Per reports on December 28, 2015, MLB cleared him as an unrestricted free agent eligble to sign with any team
During a tryout in Florida in late 2015, Hudson Belinksky of Baseball America opined that Sierra appeared "extremely polished" with a "clean arm action," easily repeating "his moderate stride.. through release.. consistently landing online and hitting his spots down in the strike zone." He threw a fastball in the mid 90s miles per hour and a slider.
On February 21, 2016, Sierra signed a six year, $30 million, contract with the Los Angeles Dodgers.