The third-year cornerback—now out for the year after tearing his ACL, according to Jon Breech of CBS Sports—isn't a star, but that doesn't mean he wasn't a valuable piece to Jim Harbaugh's secondary.
Selected out of South Carolina in Round 3 of the 2011 draft, Culliver hasn't missed a game in his NFL career and started six games in 2012. He intercepted two passes, defended 15 more, forced one fumble and had 43 total tackles, per Pro-Football-Reference.
An interesting tidbit: According to Pro Football Focus (subscription required), Culliver was actually more effective last year than Carlos Rogers, whom many have perceived to be the better cornerback.
Culliver's overall grade of 5.7 was considerably higher than Rogers' 2.1, and the former received a 6.1 rating in coverage while the latter's was 0.6.
Furthermore, Rogers allowed a 92.9 QB rating on passes thrown in his direction, while Culliver allowed a much more respectable 76.9. With age on his side, it wouldn't have been a major surprise if Culliver actually took starting snaps away from the 32-year-old Rogers in 2013.
But that possibility is now gone, so the 49ers have some secondary shuffling to do.
Without a steady rotational player like Culliver, Tarell Brown, PFF's highest-rated San Francisco cornerback in 2012, must take the next step to become one of the better secondary members in the league.
In the past, despite none of San Francisco's cornerbacks being considered elite individually, the depth in the secondary—along with the team's incredibly disruptive front seven—made the 49ers a top-tier passing defense.
A season ago, Vic Fangio's unit accumulated 38 sacks, and according to PFF, it tallied 188 quarterback hurries, the third-highest total in the NFL.
With that help, the 49ers ended the year with the fourth-fewest passing yards allowed and the sixth-lowest opponent passer rating.
Basically, as long as Justin Smith, Aldon Smith and blitzing linebackers Patrick Willis and NaVorro Bowman continue to place incessant pressure on opposing quarterbacks, San Francisco should be OK defending the pass.
But a lack of established depth could hurt as the season wears on. After all, Culliver played 691 snaps in 2012.
Nnamdi Asomugha, just two years removed from signing a five-year, $60 million deal that featured $25 million guaranteed with the Philadelphia Eagles, has suddenly become a vital reinforcement. He could emerge as the primary Culliver replacement in three-cornerback sets.
Like Rogers, he too is past his prime. But with lower expectations and the chance to play as the No. 3 corner on a much more disruptive defense, Asomugha could carve out an ideal niche.
For some perspective, the Eagles managed only 30 sacks and 160 quarterback hurries last year.
Tramaine Brock and Perrish Cox have experience in San Francisco's scheme, but Asomugha possesses more natural talent. He just needs to be utilized correctly.
Even so, losing Culliver for the entire season hurts the defensively stout 49ers. It puts a strain on a secondary that lost safety Dashon Goldson in free agency, features Carlos Rogers (in the twilight of his career) and doesn't boast desirable depth.
San Francisco's coaching staff will be tested in its handling of pass coverage, but with the serious complementary pieces elsewhere in the defense, don't expect Culliver's absence to lead to a drastic decline in the 49ers' stinginess.
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