Fooch’s note: Defensive coordinator Robert Saleh said Ray Ray Armstrong will get some first team reps as well.

The San Francisco 49ers were back at practice on Monday, and after placing linebacker Malcolm Smith on injured reserve, the team sent out Reuben Foster with the first team defense. He was getting Smith’s weak side linebacker work with the first team defense, ahead of Ray Ray Armstrong.

Foster opened training camp practicing exclusively with the third team defense. Armstrong and Brock Coyle handled second-team duties. Last week, the team wanted to get him some second team MIKE work, but a day off for NaVorro Bowman and a rib injury to Coyle resulted in Foster getting some first team work at MIKE. Coyle’s injury has kept him sidelined, and so Foster was getting more second team work prior to Smith’s injury.

The 49ers have some decisions to make about playing time this Friday when they face the Kansas City Chiefs. The 49ers could give both Foster and Armstrong some first team work, or could mix and match base and nickel work. We don’t know quite how things will shake out, with two more practices on tap for Tuesday and Wednesday. If Foster remains the first team WILL linebacker into the preseason opener, it will be a pretty big piece of the puzzle as to who is replacing Malcolm Smith.