SANTA CLARA, Calif. -- Anthony Davis, who started every game of his first four years at right tackle for the San Francisco 49ers until missing the first two of this season with a left hamstring issue, has yet to practice this week.

Jonathan Martin, acquired this offseason, had been doing a serviceable job on the right side ... until having a rough go of it in Sunday night’s 28-20 loss to the Chicago Bears.

Martin allowed two fourth-quarter sacks in the Bears’ comeback win, along with four pressures overall, to post a -1.2 grade, per Pro Football Focus.

"I thought I played well for a lot of the game," he said at the time. "That last drive is obviously not up to par. So, it’s frustrating. It’s something to improve on. Got to do better next time, next game."

Among other 49ers offensive linemen, right guard Alex Boone allowed two hurries and had a grade of -0.7 in his first start after holding out for a new contract all summer, and left guard Mike Iupati had a good game with a +1.8 grade.

49ers coach Jim Harbaugh, though, would not comment specifically on the job done by Martin.

"We could talk about a lot of guys," Harbaugh said. "There’s some really good things and things that we’ll look to improve on. We all kind of fall into that category right now after this game. We all feel like we have fingerprints on it.

"Some really good things were done by Jonathan Martin, by our offense, by our defense, by our special teams. Other things we need to improve on."