The Cubs released Armstrong on Tuesday.
The Cubs designated Armstrong for assignment Friday, Meghan Montemurro of the Chicago Tribune reports.
The Cubs claimed Armstrong off waivers Friday, Jeff Passan of ESPN.com reports.
The Cardinals designated Armstrong for assignment Tuesday, Katie Woo of The Athletic reports.
The Cardinals acquired Armstrong from the Cardinals on Tuesday in exchange for outfielder Dylan Carlson, Ken Rosenthal of The Athletic reports.
Armstrong will serve as the Rays' opening pitcher for Tuesday's game against the Blue Jays, Marc Topkin of the Tampa Bay Times reports.
Armstrong will serve as the Rays' opening pitcher for Thursday's game against the Athletics.
Armstrong will serve as an opener for Friday's game against the Royals, Marc Topkin of the Tampa Bay Times reports.
Armstrong will serve as the Rays' opening pitcher for Wednesday's game against the Tigers.
Armstrong will serve as the Rays' opening pitcher for Sunday's game against the Giants, Ryan Bass of Bally Sports Sun reports.