Head coach Shane Steichen said the Colts could also make an additional roster move at quarterback this week with Daniel Jones sustaining a season-ending Achilles' injury against the Jacksonville Jaguars.
Ralph, who led the New Palestine Dragons to back-to-back state championships for the second time in his career, has continued to achieve new heights as a coach.
Rookie quarterback Riley Leonard played three quarters in the Colts' 36-19 loss to the Jacksonville Jaguars after Jones left the game with an Achilles injury.