Acquired from the Chicago White Sox in the offseason, Santiago is 0-6 with a 5.19 ERA in seven starts. He was pulled after allowing six runs in 2 1-3 innings in a loss to the Yankees on Wednesday, and apologized to Mike Scioscia for walking off the mound before the manager arrived and not breaking stride on his way to the dugout.
No replacement starter has been announced for Tuesday, when Santiago's turn comes up next.
Navarro was in the starting lineup against the Blue Jays on Friday as the left fielder. Primarily a first baseman, Navarro has not played the outfield in two previous major league stints, but has made 11 outfield appearances at Triple-A this season.
Navarro replaces left-hander Nick Maronde, who was optioned to Triple-A Wednesday.
Bench coach Dino Ebel managed the Angels on Friday and Saturday while Scioscia attends his daughter's college graduation.