He played in Major League Baseball (MLB) for the San Diego Padres, Oakland Athletics, and New York Mets.

On July 19, 2014, Alvarez was traded to the San Diego Padres with José Rondón, Taylor Lindsey, and Elliot Morris in exchange for Huston Street and Trevor Gott.

On December 18, 2014, the Padres traded Alvarez and Jesse Hahn to the Oakland Athletics for Derek Norris, Seth Streich, and international bonus slot 117.

[13] Alvarez spent the 2018 season with Triple–A Round Rock, making 45 appearances out of the bullpen and compiling a 3.68 ERA with 44 strikeouts and 24 saves across 44 innings pitched.

[14] On November 26, 2018, Alvarez signed a minor league contract with the Miami Marlins that included an invitation to spring training.

[15] On December 20, 2019, the Boston Red Sox signed Alvarez to a minor league contract and invited him to spring training.