The Oakland A's announced on Friday that left-hander Brett Anderson, who has not pitched since April 29, has a stress fracture in his right foot.
He will be re-evaluated in four weeks, and the San Francisco Chronicle reports that means he probably won't be ready to pitch for the A's for about two months.
Anderson is 1-4 with a 6.21 earned-run average this season.
Dan Straily has taken Anderson's spot in the rotation, but he has a 7.27 ERA.
The A's called up reliever Hideki Okajima from Triple-A Sacramento and designed right-hander Chris Resop for assignment.