Analysis: 49ers defense will show improvement if big men step up

SANTA CLARA - Richard Sherman’s comeback won’t dictate how the 49ers defense performs. Nor will Reuben Foster tackling ability.

If DeForest Buckner anchors the defensive line’s necessary emergence, then the 49ers indeed have a group capable of sharing the spotlight with their Jimmy Garoppolo-led offense. Now, if it’s Arik Armstead or Solomon Thomas actually keying the defensive front, then that’ll work, too.

Meanwhile, Robert Saleh is back as defensive coordinator - the first to retain that role since Vic Fangio in 2011-14 - and his optimism will wash over players as they report Wednesday to training camp.

Here is a scouting report on each defensive unit:

DEFENSIVE LINE: DeForest Buckner, Arik Armstead, Solomon Thomas, Earl Mitchell. Backups: Jeremiah Attaochu, Cassius Marsh, Ronald Blair, Sheldon Day, D.J. Jones, Niles Scott, Kentavius Street, Jullian Taylor, Blaine Woodson.

Analysis: The honeymoon is over for the 2015-17 top picks (Armstead, Buckner and Thomas) as they must break through as a force. While Buckner has shown the most consistency on the interior, Armstead is moving from a pass-rush spot to more of a “big end” run stopper, and Thomas is going to bounce from the edge to interior. The big dilemma is who can be a reliable pass rusher, and if it’s not from that trio, then Marsh and Attaochu must emerge. Mitchell brings a veteran presence and he’ll be pushed at nose tackle by Day and Jones. While Street sits out his rookie year (knee), Taylor could be a seventh-round surprise.

OUTSIDE LINEBACKER: Eli Harold. Backups: Dekoda Watson, Pita Taumoepenu.

Analysis: Harold’s rookie contract is coming to an end so he needs to up his tally from five sacks in three seasons. Watson has special-teams prowess. Taumoepenu has bulked up some but is it enough after an invisible rookie year?

INSIDE LINEBACKER: Malcolm Smith, Reuben Foster. Backups: Brock Coyle, Korey Toomer, Fred Warner, Elijah Lee, Mark Nzeocha.

Analysis: Foster will open the season with a two-game suspension, and the 49ers can cover for him with respectable options, whether it’s plugging in veterans Coyle and Toomer or unveiling Warner, an enticing rookie. Smith has waited a year for his first contact drills, having torn a pectoral muscle early in last summer’s camp.

CORNERBACK: Richard Sherman, Ahkello Witherspoon. Backups: Jimmie Ward, K’Waun Williams, Greg Mabin, Tyvis Powell, D.J. Reed, Tarvarius Moore, Tarvarus McFadden, C.J. Goodwin, Emmanuel Moseley.

Analysis: All eyes are on Sherman’s repaired Achilles and how he moves with six weeks to rehearse for the season opener. If Sherman’s healthy, Ward’s move back to cornerback (and to the bench) is awkward considering how hard coaches sold his ability as a free safety last year, but he’s versatile and valuable. Ward might also push Williams (and Reed) as a slot corner. Powell, Mabin and Moore are poised to win roster spots, too.

SAFETIES: Jaquiski Tartt, Adrian Colbert. Backups: Ward, Reed, Antone Exum, Chanceller James, Don Jones, Terrell Williams.

Analysis: The NFL shouldn’t sleep on this safety tandem of Tartt and Colbert, who are physical and rangy with instincts to attack the ball. Colbert unseated the oft-injured Ward last season as a high-intensity rookie. James looked sharp last summer before a knee injury so his return will be worth watching.