The San Francisco 49ers will be without one of their key defensive players for a while after tackle Arik Armstead sprained his right knee in the team's first practice of training camp on Wednesday.

Armstead appeared to suffer the injury when he collided with an offensive lineman early in team drills in Wednesday's practice. "He thought it was just a bruise because it didn't bother him that bad but it was hurting him more after and we got the MRI, and so we've got to hold him out for a little bit," coach Kyle Shanahan said. According to Shanahan, Armstead is likely to miss "a few weeks" but the injury isn't something the team is concerned about for the long term. Armstead entered this training camp with a bit more clarity on his position than he's had in recent seasons. After the Niners used him as a defensive end on early downs and moved him inside in pass rush situations, Armstead moved to defensive tackle full time in Week 8 after an injury to tackle Javon Kinlaw. The results were strong as Armstead finished fourth at his position in tackles (46) and tied for ninth in sacks (4) in that span. He carried that over into the postseason with three sacks in as many games as the Niners went to the NFC Championship Game. All of that led to Armstead finding a home on the interior to open this camp, a move he has embraced because it allows him to be more involved from play to play. "I'm definitely looking forward to it," Armstead said Tuesday. "I think it will be good. I'm excited for it and I think I can dominate in this role as well." While Armstead will miss some time, the Niners are expecting to welcome back another pair of key contributors. Shanahan said Kinlaw and offensive tackle Mike McGlinchey, both of whom have been recovering from injuries suffered last season, are slated to join team drills starting Saturday.