Arik Armstead began the hitting a day early.
The 49ers’ first fully padded practice of 2016 is Tuesday, but during Monday’s session, Armstead broke through the left side of the offensive line and crashed – accidentally – into running back Carlos Hyde, causing a fumble. A few plays later, the 6-foot-7 defensive lineman again was in the backfield to thwart another running play.
“That’s the name of the game, making plays, so that’s what I’m trying to do,” Armstead said.
Armstead, who was drafted 17th overall last year, likely will start when the season opens Sept. 12 against the Los Angeles Rams at Levi’s Stadium. Figuring out the rest of the defensive front seven is more difficult.
Never miss a local story.
One top candidate, outside linebacker Aaron Lynch, is suspended for the first four games for violating the league’s substance abuse policy. Another, nose tackle Ian Williams, is out for the season because of an ankle injury. A third, veteran lineman Glenn Dorsey, is coming back from an ACL injury in November.
Defensive coordinator Jim O’Neil said the team’s depth chart currently is “written in sand.”
“We’ll find out a lot more in the next week or two,” O’Neil said. “Sometimes, there’s two or three guys you love in shorts and they don’t show up with the pads on, and then there’s two or three guys that you don’t necessarily like with the shorts on and then the pads go on and you’re like, ‘Wow, where did he come from?’ ”
On Sunday, for instance, the 49ers’ first-string defensive line had Armstead on the left side, Mike Purcell at nose tackle and Quinton Dial at right defensive end. A day later, first-round draft pick DeForest Buckner was on the left, Dial was in the middle, and Armstead was on the right, where he proved to be a tough match up for left guard Zane Beadles.
The linebacker spots also are in flux.
NaVorro Bowman is locked into one of the starting roles at inside linebacker. But Michael Wilhoite practiced next to him Sunday, Gerald Hodges was there Monday, and Ray-Ray Armstrong will get a chance during Tuesday’s session.
At outside linebacker, Lynch and veteran Ahmad Brooks have received most of the first-team snaps. The candidates to replace Lynch are second-year player Eli Harold, Tank Carradine, Corey Lemonier and fifth-round draft pick Ronald Blair, who mostly has been used as a defensive lineman in training camp.
“It’s an opportunity for some guys to step up,” O’Neil said. “We’re going to play the best 11. So if it’s two outside backers and three D-linemen, if it’s four D-linemen, one outside backer, if it’s three D-linemen, an outside backer and an inside backer, we’re going to get the best 11 out there. … We can do a lot of things package-wise in the first quarter of the season to absorb some of the reps that we’re going to lose from Aaron.”
Armstead, meanwhile, is building off a promising rookie season in which he played 33 percent of the defensive snaps and routinely collapsed the pocket on pass plays. He finished with two sacks and, according to scouting service Pro Football Focus, had 38 total pressures.
Armstead appears to be in even better physical shape this season. He said he especially looks forward to his full-contact meetings with tackle Joe Staley, the most technically sound and athletic of the 49ers’ offensive linemen.
“He forces you to have good footwork and good anticipation,” Armstead said. “Other guys do other things well. There are stronger guys, guys who like to grab, so you have work off people trying to grab you. I like playing against all of them and just getting better, and I know it will pay off during the year.”