***UPDATE*** Anthony Davis indeed is out for the upcoming game. Jim Harbaugh also said Alex Boone would be activated Saturday. He did not say whether Boone would start the game against the Cowboys.
SANTA CLARA -- It appears Anthony Davis will miss his third straight practice with a hamstring injury, making it likely that Jonathan Martin will start at right tackle for the 49ers in Dallas on Sunday.
Martin played every preseason game at the position, and he played a little left tackle as well. He’s gotten progressively better -- and stronger -- the further he’s gotten from his bout with mononucleosis that sidelined him in the spring.
“I think he’s definitely made strides there,” offensive coordinator Greg Roman said Thursday. “He lost a bunch of weight and a lot of the gains he had put together, he had to start back at square one once he got over that little illness.”
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Davis’ absence also would mean that Alex Boone likely would be in uniform for the game on Sunday. That’s because Boone can play both guard and tackle and would be the fill in if either Martin or left tackle Joe Staley is hurt. Boone also could start at right guard or he could be held in reserve while Joe Looney starts at right guard.
The team currently has a roster exemption for Boone; if he plays Sunday they would have to cut one of the players on the squad to make room for him.
Meanwhile, Ray McDonald was on hand for the start of practice. The team’s starting left defensive end had been a late arrival -- no explanation given why -- for Wednesday’s and Thursday’s sessions. Michael Crabtree (calf), Chris Culliver (ankle) and Vance McDonald (hamstring) also were present for the start of practice.