WHAT'S GONE RIGHT
Interior line play: For the most part, it has been stellar. Except for one quarter against Denver, the Niners have been very strong against the rush and winning the battle at the line of scrimmage.
Improved pass rush: Ends Andre Carter and Chike Okeafor are becoming a menacing pair that must be reckoned with. The Niners also are getting production in this department from Julian Peterson and other blitzing linebackers. With 10 sacks through three games, they are on a pace to have 53 this season. They had 32 last year.
Development of young linebackers: Jamie Winborn has displayed star potential, and Peterson also is coming along quite nicely in his third season.
Keeping opponents off the scoreboard: Both of San Francisco's wins were a product of limiting the opposition's point production. The Niners rank sixth in the NFL in points allowed.
Tony Parrish fitting in: The starting strong safety has come in and made his impact felt immediately in the secondary.
WHAT'S GONE WRONG
Injuries, mostly: Winborn, who had become an integral part of the defense, could be out as long as two months with a knee injury, though he'll likely return sooner. Injuries also have slowed linebacker Jeff Ulbrich and defensive tackle Jim Flanigan, who both play key roles on this defense. Several other players also have been hampered by various ailments.
Third-down conversions: After forcing opponents into third-down situations, the Niners have been letting them off the hook much too often. San Francisco is 28th in the league in third-down efficiency, meaning opponents are extending drives against them on a frequent basis.
WHAT NEEDS TO CHANGE
Shore up coverage units: The Niners have played well in the secondary, but they still need to improve in third-down passing situations when they have extra defensive backs on the field.
Continue mixing it up with linebackers: The Niners have done a great job of getting the most out of their talented linebacker corps with blitzes and stunts and moving players such as Peterson around in various formations.
Attack more: The Niners still play a read-and-react type of defense. They have the talent and experience now to take it to opponents much more frequently - no matter how they're offense is playing.