Soria was injured while giving up a grand slam to Hunter Renfroe in the ninth inning Thursday in an 8-4 home loss to San Diego. He left the after facing two batters.
"We'll just treat it and maybe by the end of the weekend we'll have a better idea," manager Craig Counsell said.
Soria has a 1.59 ERA in seven games since Milwaukee acquired him in a trade two weeks ago with the Chicago White Sox. In 40 games overall, he is 0-3 with a 2.44 ERA and 16 saves in 20 chances.
The Brewers recalled right-hander Adrian Houser from Triple-A Colorado Springs to replace Soria.
Struggling closer Corey Knebel was not available Friday against the Atlanta Braves after giving up four runs, two hits and four walks in the last two games. Counsell said Josh Hader would fill the role.
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