Kyle Shanahan concerned about Arik Armstead after 49ers rule him out

The 49ers ruled out defensive tackle Arik Armstead (foot, knee), linebacker Oren Burks (knee), tight end Ross Dwelley (ankle) and receiver Jauan Jennings (concussion) for Monday's game against the Ravens.This will be the third consecutive game Armstead has missed. His foot injury is a concern given it's similar to the foot injury he battled through last season."Yes, we're concerned," 49ers coach Kyle Shanahan said Saturday, via David Bonilla of 49erswebzone.com. "We do think he has a chance each week, but I'd say it's a little more the foot than the knee, something that's bothering for a little bit. I'm just hoping the pain will go down."Armstead has 27 tackles, five sacks and 13 quarterback hits in 12 games.The 49ers list defensive tackle Javon Hargrave (hamstring) and running back Elijah Mitchell (knee) as questionable.