Bruce Chen (back) isn't close to beginning a rehab assignment. Chen, who is nursing a bulging disk in lower back, threw a more intense bullpen session Saturday, but he's still got a ways to go. "I don't imagine it's going to be in the next four, five, six, seven days" that he takes a mound in a minor-league game, Royals manager Ned Yost said. With Danny Duffy pitching well, Chen might not have a rotation spot waiting for him once he's ready.