Arik Armstead pushing through shoulder injury

SANTA CLARA, Calif. -- The San Francisco 49ers’ lengthy injury report on this short week again includes second-year defensive tackle Arik Armstead.

Armstead has been an early-season mainstay on the injury report because of a shoulder injury that has lingered since the preseason. In the early portion of training camp, Armstead appeared poised for a breakout season, but he's continued to play through the shoulder issue and it's limited how much he can be on the field and how much he produces when he is.

“I just think he’s missed a lot of football," coach Chip Kelly said. "So, that’s what I kind of look at it as. You know, he missed an extended period of time in camp. He was playing really well and then was out. This is a sport you have to practice and you have to train at. It’s very difficult just to take time off and then go out there and expect him to play at an extremely high level that he’s capable of playing because of his athletic ability and what a good football player he is. So, I think he’s just coming back into that right now, to be honest with you.”

Armstead has played 104 snaps in the first four games, which ranks fourth among San Francisco defensive linemen. How that changes this week will depend on what becomes of DeForest Buckner. Buckner has played more than any other Niners defensive lineman (173 snaps) but suffered a foot injury last week against Dallas that has left him in a walking boot during practice.

Niners defensive coordinator Jim O'Neil expressed optimism about Buckner being able to play Thursday but he was listed as a non-participant in practice for the second day in a row Tuesday.

Here's the complete Tuesday injury report, keeping in mind that San Francisco simply did a walkthrough so the injury report is based on an estimate of how much players would have participated in a normal practice:

Did not participate: LB NaVorro Bowman (achilles), DT DeForest Buckner (foot), CB Jimmie Ward (quadricep).

Limited participation: G Zane Beadles (ankle), CB Chris Davis (quadricep), WR Jeremy Kerley (ankle), TE Vance McDonald (hip).

Full participation: DT Arik Armstead (shoulder), S Marcus Cromartie (ankle), DT Quinton Dial (knee), DT Glenn Dorsey (knee), DT Mike Purcell (ankle), CB Keith Reaser (ankle), S Jaquiski Tartt (knee), G Andrew Tiller (ankle).