49ers defensive line star Arik Armstead suffers knee injury at practice

SANTA CLARA (CBS SF) — The San Francisco 49ers have lost standout defensive lineman Arik Armstead for at least a few weeks after he suffered a knee injury during practice at training camp.

Head coach Kyle Shanahan revealed the injury — which happened on Wednesday — at this Friday morning news conference and hoped his star defender would not be sidelined for long.

“(We) thought it was just a bruise because it didn’t bother him that bad, but it was hurting a little after and he got the MRI,” Shanahan told reporters “We’re going to hold him out for a little bit.”  

NBC Sports Bay Area was reporting that Armstead had suffered a partially torn medial collateral ligament.

Ironically, it was Javon Kinlaw’s season-ending ACL tear last year that forced Armstead from defensive end to defensive tackle. He responded with six sacks and a career-best 63 tackles in 17 regular-season games.  

Over the last week, the team had signed two veteran free agent defensive linemen — Robert Nkemdiche on Monday and Tomasi Laulile on Friday.

While Laulile is a journeyman, Nkemdiche has plenty of playing experience.

Nkemdiche  was originally drafted by the Arizona Cardinals in the first round of the 2016 NFL Draft. Throughout his five-year career with the Cardinals, Miami Dolphins and Seattle Seahawks, he has appeared in 38 games and registered 59 tackles, 4.5 sacks, three passes defensed, two forced fumbles and one fumble recovery.  

Last season with the Seahawks, Nkemdiche appeared in nine games and finished with 15 tackles and one pass defensed.

“He’s (Nkemdiche) come in, he had a really good workout for us,” defensive coordinator DeMeco Ryans told reporters on Thursday. “He’s come in, he’s figuring it out, like I said. When you come into our system with our defense line, it’s a different style. It’s a different technique than most guys have done in their careers, so it takes time. It takes time to get used to it. It takes time and you have to put in the work each and every day.”

Charles Omenihu subbed in for Armstead at Thursday’s practice. When Ryans made his comments, he was well aware of Armstead’s injury. He told reporters the team has a lot of depth long the defensive front.

“I think all along our defensive line, we’ve got a lot of depth on our defensive line,” he said.  “A lot of those guys have been here… Charles is coming along, he’s competing, he’s another year in our system, he’s doing much better. Understanding the techniques and what we’re asking of him and just the competition level there. “

“We talked about the DB room, but also in the D-Line room,” Ryans continued. “We have a lot of competition, a lot of guys getting better each and every day, a lot of guys pushing each other and that’s what you want to see here in camp, so a lot of guys doing really well there.”