The three-game series, which was set to begin Friday at Miller Park, never got underway as the Cardinals deal with a COVID-19 outbreak.
The Cardinals will now play a four-game set against the Detroit Tigers that will run Tuesday to Thursday, with a scheduled doubleheader on Wednesday. While all four games will take place at Comerica Park, St. Louis will act as the home team for two contests.
Meanwhile, the Brewers will continue their season as scheduled.
On Saturday, the Cardinals reportedly had their sixth positive test. The team confirmed two of the cases are members of its 58-person traveling group that includes coaches and trainers.
The doubleheader was the result of an earlier coronavirus-related postponement.
News of the postponement comes shortly after a report that commissioner Rob Manfred warned MLBPA executive director Tony Clark that the season could be canceled if players don't better follow pandemic protocols.
The report indicates that the league and players both believe this weekend's series will be crucial in the commissioner's decision on whether to continue the 2020 campaign.