SANTA CLARA -- Rookie linebacker Reuben Foster was promoted into the starting lineup with the season-ending injury to veteran Malcolm Smith.

The 49ers have reason to expect him to remain a starter for a long, long time.

Coach Kyle Shanahan on Tuesday said Foster was the starter at the team’s weakside linebacker position, alongside NaVorro Bowman. But he added, tthe onus is on Foster to hold onto that position.

“He could get beat out at any time,” Shanahan said. “If our guys behind him, we’ve got some good players behind him too, if they started performing at a higher level than him, then that wouldn’t be the case.”

The 49ers released their unofficial depth chart ahead of Saturday’s exhibition game against the Denver Broncos. The depth chart does not reflect the team’s decision to switch seventh-round draft pick Adrian Colbert from cornerback to free safety.

Also, veteran Tim Barnes is listed at left guard. He started all 32 games the past two seasons with the Rams at center. He is the team’s backup center, but his ability to also fill in at guard could determine whether he wins a spot on the 53-man roster.

The depth chart does not list nickel back or slot receiver. K'Waun Williams is ahead of Will Redmond as the nickel back, and Jeremy Kerley is ahead of Trent Taylor as the team's slot receiver.

Guard Joshua Garnett and safety Jimmie Ward are listed as starters despite being unavailable due to injuries. Garnett is expected back near the start of the regular season after undergoing arthroscopic surgery to clean up cartilage in his knee. Ward remains on physically unable to perform while rehabbing from a hamstring injry.

OFFENSE

WR: Pierre Garçon, Jeremy Kerley, Trent Taylor/Aaron Burbridge, DeAndre Smelter/Kendrick Bourne

LT: Joe Staley, John Theus, Darrell Williams

LG: (Joshua Garnett), Zane Beadles, Tim Barnes, Erik Mangnuson

C: Daniel Kilgore, JP Flynn

RG: Brandon Fusco, Norman Price, Andrew Gardner

RT: Trent Brown, Garry Gilliam, Andrew Lauderdale

TE: Vance McDonald, George Kittle, Logan Paulsen/Blake Bell, Garrett Celek/Cole Hikutini

WR: Marquise Goodwin, Aldrick Robinson, Victor Bolden/DeAndre Carter, Tim Patrick/Louis Murphy

RB: Carlos Hyde, Tim Hightower, Joe Williams/Kapri Bibbs, Raheem Mostert/Matt Breida

FB: Kyle Juszczyk, Tyler McCloskey

QB: Brian Hoyer, Matt Barkley, C.J. Beathard, Nick Mullens

DEFENSE

LDE: Arik Armstead, Elvis Dumervil, Aaron Lynch, Ronald Blair

LDT: Earl Mitchell, Quinton Dial, D.J. Jones

RDT: DeForest Buckner, Chris Jones, Noble Nwachukwu, Leger Douzable

RDE: Tank Carradine, Solomon Thomas,

SAM: Ahmad Brooks, Eli Harold, Dekoda Watson, Pita Taumoepenu

MIKE: NaVorro Bowman, Brock Coyle, Donavin Newsom

WILL: Reuben Foster, Ray-Ray Armstrong, Austin Calitro, Sean Porter

LCB: Rashard Robinson, K’Waun Williams/Will Redmond, Prince Charles Iworah, Asa Jackson

RCB: Dontae Johnson, Keith Reaser, Ahkello Witherspoon/Will Davis, Adrian Colbert

FS: (Jimmie Ward), Vinnie Sunseri, Lorenzo Jerome

SS: Eric Reid, Jaquiski Tartt, Don Jones

SPECIAL TEAMS

P: Bradley Pinion

K: Robbie Gould, Nick Rose

H: Bradley Pinion

PR: Jeremy Kerley, DeAndre Carter/Trent Taylor

KOR: Raheem Mostert, Victor Bolden

LS: Kyle Nelson