49ers' Anthony Davis, Michael Crabtree not on hand for start of practice

SANTA CLARA - Anthony Davis, who hasn’t missed a start in four seasons with the 49ers, was in the team’s weight room when practice began this afternoon. That raises the possibility that Jonathan Martin would start at right tackle in the team’s opener in Dallas on Sunday.

Davis had surgery in April and last month was cleared to resume practice. He went through individual drills with the team over the last week and a half of the preseason. He did not appear in any preseason games.

Davis has said he feels better than he did even before the injury. He also said he didn’t feel like he needed to play in the preseason to be ready for the Cowboys.

Receiver Michael Crabtree also was in the weight room when practice began. Crabtree had been dealing with a minor muscle strain in the preseason but he played in the team’s third game Aug. 24.

Crabtree is from the Dallas area, and it’s likely that only a serious issue would keep him from playing Sunday.

Meanwhile, outside linebacker Aldon Smith was in the weight room with the rest of his injured teammates. Smith is suspended for the first nine games of the season but can train at the team facility and attend meetings.

Defensive end Ray McDonald, who is being investigated after an arrest for suspicion of domestic abuse, was missing at the start of practice but jogged onto the field after 20 minutes. The district attorney currently is looking into whether it will charge McDonald.