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The move, made Sunday before the Angels played the New York Yankees, is retroactive to July 9.
Walden has been struggling of late. He gave up five runs in four appearances since July 1 after allowing only three runs over nine appearances in June. He is 2-2 with a 3.86 ERA in 31 appearances overall.
Walden says his shoulder was bothering him and compensation for that caused the biceps injury right before the All-Star break.
Outfielder Kole Calhoun has been recalled from Triple-A Salt Lake to take Walden's roster spot. Calhoun's bags were lost en route, and he had to borrow cleats and a glove for Sunday's game.