Farrell was designated for assignment by the Cubs on Saturday.
Farrell and Rob Zastryzny were removed from the 40-man roster to clear space for Terrance Gore and Taylor Davis. The 27-year-old has a career 5.17 ERA in 44.1 major-league innings, though his 3.64 ERA for Triple-A Iowa could be enough for another team to claim him off waivers.