The Cubs selected Crow-Armstrong's contract from Triple-A Iowa on Monday.
Jeff Passan of ESPN.com reported earlier that Crow-Armstrong would likely be activated Tuesday, but the Cubs will make the 21-year-old outfielder's promotion official ahead of Monday's series opener versus the Rockies. The lefty-hitting Crow-Armstrong is not in the lineup Monday against southpaw Kyle Freeland, but Crow-Armstrong should play regularly in center field when the Cubs oppose right-handers. Between stops at Iowa and Double-A Tennessee this season, Crow-Armstrong hit .283 with 20 home runs and 37 stolen bases over 500 plate appearances.