Toussaint will start Sunday's game against the Athletics, Daryl Van Schouwen of the Chicago Sun-Times reports.
The right-hander will fill the rotation spot of Michael Kopech, who is having his turn skipped for rest purposes. Toussaint threw just 33 pitches over 2.1 frames during his previous outing June 27 but should still be fairly stretched out given his role as a long reliever.