Keller cleared waivers Wednesday and elected to become a free agent, Daryl Van Schouwen of the Chicago Sun-Times reports.
Keller was DFA'd by the White Sox on Sunday after posting a 4.86 ERA and 1.38 WHIP across 16.2 innings, and he'll now try his luck on the open market rather than accepting an outright assignment to Triple-A Charlotte. The 28-year-old righty has not found much consistent success throughout his past few seasons in the majors, but he should have no problem securing at least a minor-league deal with another team in need of rotation depth.