A fourth-round pick of the White Sox in 2012, Brennan elected free agency on November 2 and was signed by the Colorado Rockies 11 days later. The 27-year-old has a 25-34 record with a 4.64 ERA in 172 games at all levels of the White Sox organization.
In late 2015, Brennan was assigned to Chicago’s 40-man roster to help protect him from the Rule 5 Draft. He progressed to Double-A the next season and spent the next two campaigns bouncing between Double- and Triple-A.
He had just four games at Triple-A Charlotte last season, throwing just five innings.