Cameron was walking in the outfield during batting practice when he was struck on the left thumb by a batted ball, fracturing it.
Cameron threw a bullpen session Thursday, but another player had to be used to catch the return throws from the catcher. While the injury does not affect Cameron's throwing, his timetable for a return to game action figures to hinge on when he is able to field his position without risking further injury.
"He just can't get his fingers in his glove right now," acting manger Craig Colbert said.
Mark Thoma is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.