The Cardinals outrighted Zimmermann to Triple-A Memphis on Sunday.
Zimmermann's stint on the Cardinals' 40-man roster lasted less than one day. The southpaw was called up from Triple-A ahead of Tuesday's doubleheader versus the Brewers, only to get designated for assignment ahead of Game 2 after allowing three earned runs over five innings of long relief in Game 1. Now that he's cleared waivers, Zimmermann will remain in the organization and is expected to resume working out of the rotation at Memphis.