[4] On August 8, 2009, Castro signed a minor league contract with the Tampa Bay Rays.

[6] Castro signed with the Lincoln Saltdogs of the American Association of Independent Professional Baseball for the 2010 season.

[9] Castro signed with the Fukuoka SoftBank Hawks of Nippon Professional Baseball for the 2012 season.

He only made three appearances for the Hawks' main club, recording a 6.00 ERA with two strikeouts in three innings of work.

[10] On December 7, 2012, Castro signed a minor league contract with the Los Angeles Dodgers.

In 25 games (19 starts) for the Triple–A Albuquerque Isotopes, he registered an 8–5 record and 3.48 ERA with 91 strikeouts across 116+1⁄3 innings pitched.

[14] Castro made 26 appearances (14 starts) for Memphis, logging a 9–6 record and 4.01 ERA with 63 strikeouts across 94+1⁄3 innings pitched.

[18] In 5 appearances for Oakland during his rookie campaign, Castro recorded a 2.25 ERA with 4 strikeouts across 4 innings pitched.

On March 4, 2018, Castro signed with the Bravos de León of the Mexican Baseball League.

On June 26, 2022, after three years of inactivity, Castro signed with the Toronto Maple Leafs of the Intercounty Baseball League.