"Each team we check in with has the starters in base packages alongside a select group of players who are likely to be key contributors in a rotation, sub-package, or as competition in training camp for some incumbent starters," said Ben Stockwell of Pro Football Focus. "The 49ers allowed 5.13 yards per carry in sub packages last season, the fourth-worst mark in the NFL."
They also listed DE Arik Armstead, DE Glenn Dorsey, OLB Eli Harold, OLB Corey Lemonier, and ILB Michael Wilhoite as other names to know.
"Led by Ian Williams, the 49ers' base run defense is in safe hands, but they allowed nearly 2 yards per carry more in sub-packages than base, the biggest drop-off in the league last year," explained Stockwell. "While the addition of Buckner to pair with former Oregon teammate Arik Armstead adds to their interior pass-rush, the 49ers' sub-package run-D has to raise its game in 2016, Williams is the key to the 49ers' run defense, and teams can remove him from the equation without blocking him, simply by forcing San Francisco into their nickel and dime defenses. Another year removed from a devastating knee injury, San Francisco will hope that NaVorro Bowman can be close to his old self in coverage after he allowed the most yards and broke up the fewest passes in a single season since he entered the starting lineup last year."