Lopez (back) was reinstated from the 15-day injured list ahead of Game 2 of Tuesday's doubleheader against the Royals, Daryl Van Schouwen of the Chicago Sun-Times reports.
Lopez suffered the injury during his first appearance after the All-Star break, but he's now been cleared to rejoin Chicago's active roster. The 28-year-old has been a key bullpen piece for the White Sox this year with a 2.98 ERA, 1.06 WHIP and 44:8 K:BB across 42.1 innings.