Osorio returns to the lineup after starting TFC's first four playoff matches, though Johnson got the nod for the Eastern Conference semifinal second leg against the Montreal Impact.
The Seattle Sounders, meanwhile, have Osvaldo Alonso and Erik Friberg in the lineup, despite lingering injuries that left their participation in question.
Here are the lineups in full:
Toronto FC: Irwin; Zavaleta, Moor, Hagglund; Beitashour, Cooper, Bradley, Osorio, Morrow; Giovinco, Altidore
Subs: Bono, Williams, Bloom, Cheyrou, Johnson, Endoh, Ricketts
Seattle Sounders: Frei; Mears, Torres, Marshall, Jones; Alonso, Roldan; Lodeiro, Friberg, Morris; Valdez
Subs: Miller, Scott, Fisher, Evans, Ivanschitz, Fernandez, Gomez