"It's going to be four to six weeks," manager Bruce Bochy said last night. "He can swing a bat but can't throw."
Jeff Cirillo, who suffered the injury Monday on a bunt attempt against Texas, will likely head to the disabled list when the team sets its opening-day roster.
San Diego is slated to open the season Monday in Los Angeles.
Cirillo was acquired in an off-season trade with Seattle. Last year, he batted just .205 with two homers and 23 RBI in 87 games.
Cirillo batted .157 in 51 at bats this spring, but was 7-of-24 after going 1-for-27 to start the spring.
It is unclear who will take his spot on the opening day roster.