Bernard Dotson has played showman-lawyer Flynn since Usher's departure. Usher had played Flynn from Aug. 22 until Oct. 6 when he became ill.
On Sunday, Christopher McDonald assumes the Flynn role at Broadway's Ambassador Theatre, Broadway.com reports.
"Usher is currently being treated for an extreme case of strep throat," manager Jonnetta Patton said. She added that Usher was "under strict orders from his doctors" not to perform.
"Chicago" Producer Barry Weissler told Broadway.com, "The entire "Chicago" company is sending their thoughts and best wishes to Usher for a quick and speedy recovery."
Critical response to Usher's appearance was mixed, with his singing and dancing receiving better reviews than his acting.