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The 49ers are known for having a punishing defense, as Patrick Willis, NaVorro Bowman, Aldon Smith and other defensive stars reside in San Francisco.
However, San Francisco isn't exactly a defensive juggernaut just yet. There are question marks in the secondary, as safety Donte Whitner didn't exactly flourish in 2012, and first-round draft pick Eric Reid is unproven. As for the corners, the 49ers don't have much quality depth behind their two starters.
Chris Culliver was burned in coverage often last season, and Carlos Rogers was a liability. Tarell Brown stepped up for the most part, but he gave up some big plays as well. Nnamdi Asomugha may end up rekindling his dominance from Oakland, but he's aging and coming off of a horrendous stint in Philadelphia.
In other words, if the 49ers don't apply pressure on the quarterback, the secondary will collapse and the defense will surrender points.
Aldon and Justin Smith will both help the 49ers apply pressure on the quarterback, as Justin can absorb defenders and create blitzing lanes for Aldon. Aldon led the NFC with 19.5 sacks, and he has perfected a multitude of moves to help him get to the quarterback more effectively.
Ahmad Brooks is in hot water with the law, but he may not miss any time, according to Gregg Rosenthal of NFL.com. If he plays, the 49ers will have a dominant tandem of pass-rushing outside linebackers. Even if Brooks misses time with a suspension, the 49ers will be fine.
Parys Haralson, who has been with the 49ers for seven years, is back from an injury, and rookie Corey Lemonier, who registered 15 sacks in his final 21 college games, has a chance to do something big.
As for the linebackers, there aren't any better middle linebackers in the game. Bowman and Willis combined for 268 tackles in 2012, and Willis finished second among middle linebackers with nine passes defensed.
San Francisco's linebackers will continue to dominate in all facets of the game, and the defensive line will do its part. However, there is uncertainty in the secondary. If Asomugha can't become the shutdown corner who was rarely targeted in Oakland, the 49ers will have trouble stopping potent aerial attacks.
In a pass-heavy league, that's not a good thing.
Overall, the defense is solid, and it deserves a look in the draft. It should be one of the first defenses targeted, as it allowed the second-fewest points in the NFL last season. However, if the secondary's problems aren't solved, it will cause a conflict in San Francisco.
The defense should be targeted around the 10th or 11th round, but it shouldn't be counted on to lead a fantasy team. There are question marks, and that could lead to a dip in production from the group.