SANTA CLARA -- Outside linebacker Cam Johnson, who has rarely practiced since coming to the 49ers as a seventh-round draft pick, wore shoulder pads Tuesday and appeared ready to take part in practice.Johnson has been out since early in training camp with a knee injury. He underwent a surgical procedure in the offseason, too. Johnson has not participated in the 49ers' first three exhibition games. It is not known if Johnson would go through a full practice. The team's practices are closed to the media.Outside linebacker Parys Haralson was not on the practice field. His injury or status was not immediately known.Also, outside linebacker Eric Bakhtiari, who sustained a concussion in Sunday's game at Denver, wore a black jersey to signify to his teammates to avoid contact with him.Other 49ers who were not on the practice field Tuesday: tight enddefensive lineman Demarcus Dobbs (left leg), running back Brandon Jacobs (left knee), receiverreturn man Ted Ginn (right ankle) and receiver Mario Manningham (bereavement). Manningham's grandfather died last week. He is not expected to rejoin the team until after Thursday's funeral.