Estrada was a starting rotation fill-in as things stood to begin with. He took the place of Chris Narveson, who is out for the season with a torn rotator cuff.
Estrada, 28, is 0-3 with a 4.50 ERA and 1.11 WHIP this season.
As a corresponding move, the Brewers recalled relief pitcher Mike McClendon, meaning Manny Parra is likely to fit in the rotation until Estrada can return.
Parra, 29, has a 3.70 ERA and 1.36 WHIP in 24 1/3 innings this season out of the Milwaukee bullpen. He was a starter earlier in his career but sports a 5.44 ERA and 1.69 WHIP in 74 career starts. The lefty hasn't started a major-league game since 2010.
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