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Carlos Rogers is beaten for a touchdown
Good pass defense is the result of a strong pass rush and good coverage from the secondary and linebackers. I have already discussed how the 49ers' pass rush needs to be more consistent. That alone would hide some of the flaws in the 49ers' pass defense.
The 49ers' linebacker corps is the strength of the team. Inside backers Patrick Willis and NaVorro Bowman are strong and fast, two of the best in the league. Along with Ahman Brooks, they do a good job in pass coverage.
The question is in the 49ers' defensive secondary, particularly Carlos Rogers. He and Dashon Goldson were tied for the team lead with six interceptions last year. However, in 2012, Rogers has yet to get a pick.
The real issue, however, is that Rogers has had major problems and the 49ers have been slow to adjust. He struggles against the quicker, more elusive receivers, which was evident against the Giants and Rams.
In the 2011 NFC title game, Victor Cruz torched Rogers for 10 catches and 142 yards. Then, when the two teams met earlier this year, Cruz again was a key force in the New York offense, with six receptions for 58 yards and a touchdown.
The 49ers' game against the Rams also showed how a team with a quick, shifty receiver can victimize Rogers. Danny Amendola, who is a good receiver but not in the same class of Cruz, lit up the 49ers with 11 catches for 102 yards. Most of those receptions were against Rogers.
Amendola also had another huge play against Rogers called back in overtime, due to a penalty. Had the flag not been thrown, the Rams would have won the game.
When teams play a three-receiver set, Rogers is on the slot receiver. The 49ers like him there because he is a good tackler and experienced in traffic. However, this often matches him up against the opponent's quickest receiver.
Defensive coordinator Vic Fangio may need to switch nickel back Chris Culliver inside and move Rogers to the outside against this formation. The 49ers can't continue to allow players like Cruz or Amendola to have big games.
The other members of the 49ers' defensive backfield—Tarell Brown, Donte Whitner and Goldson— have been solid. The weak link has been Rogers, who had a Pro Bowl year in 2011.
If the 49ers are to have the best chance of winning the Super Bowl, the secondary must be more consistent. That is particularly true of Rogers.