Supak signed a minor-league deal with the A's and received an invitation to spring training.
Supak elected free agency Monday.
Supak cleared waivers and was outrighted to Triple-A San Antonio on Wednesday, Todd Rosiak of the Milwaukee Journal Sentinel reports.
The Brewers designated Supak for assignment Monday.
Supak was optioned to the Brewers' alternate training site Tuesday.
Supak was recalled from the alternate training site Monday.
Supak was added to the Brewers' 60-man roster Thursday.
Supak was optioned to minor league camp Monday.
Supak was promoted to Triple-A San Antonio on Friday, Todd Rosiak of the Milwaukee Journal Sentinel reports.
Supak fell one out short of a no-hitter Tuesday for the second time this season.