Chen isn't sure how much time he will miss. Through an interpreter, he said, "The only thing I can do right now is help myself and get better and not do anything to get worse."
Signed as a free agent in January 2012 after starring in Japan, the native of Taiwan made 32 starts for Baltimore last year and is 3-3 over eight starts this season.
Also Tuesday, the Orioles recalled right-handed reliever Alex Burnett and infielder Yamaico Navarro. Burnett appeared in one game with Baltimore earlier this month.