He split 2009 between the Dunedin Blue Jays and New Hampshire Fisher Cats, hitting a combined .292 with 6 home runs and 62 RBIs.

[2] Sierra was brought up to the Toronto Blue Jays on July 31, 2012, following the trades of Travis Snider and Eric Thames.

[4][5] On August 13, Sierra hit his first career home run, a solo shot off Chicago White Sox starter Jake Peavy.

[10] Sierra found regular time as a reserve outfielder for the White Sox in 2014, hitting .279 with two home runs, before going on the disabled list with a strained oblique on August 16.

[16] He spent the 2017 season with the Triple–A New Orleans Baby Cakes, playing in 123 games and hitting .294/.361/.438 with 11 home runs, 68 RBI, and 18 stolen bases.

On December 5, 2019, it was announced that Sierra had signed with the Chunichi Dragons of Nippon Professional Baseball League (NPB) on a development contract.

[25] On March 4, 2021, Sierra signed with the Tecolotes de los Dos Laredos of the Mexican League.

[26] On February 28, 2022, Sierra signed with the Wild Health Genomes of the Atlantic League of Professional Baseball.

On February 20, 2023, Sierra signed with the Spire City Ghost Hounds of the Atlantic League of Professional Baseball.