Yes, there are problems with the offense. Yes, Colin Kaepernick has regressed in his second season starting under center. Yes, there have been injuries.
All of the aforementioned circumstances are well documented.
We also know the 49ers have based their 2013 approach on two basic schemes—a power running game and a stalwart defense.
What about that defense?
In spite of San Francisco's recent woes, the defense has remained one of the signature aspects of this franchise.
The 49ers' dominance on defense is nothing new to San Francisco and its fans. The defense has long been regarded as a primary reason behind the 49ers' rise to prominence over recent years. During the team's struggles in 2013, the defense is often the sole unit holding the 49ers together.
Let us take a look at how the 49ers defense got here and where they expect to go moving forward.
The Pre-Harbaugh Years
This should be a review for most 49ers fans.
Building up to 2011—the year that head coach Jim Harbaugh took over the team—the 49ers were a talent-laden team that struggled to put all the pieces together to compete within the NFC.
As a result, San Francisco was able to stockpile a number of high-value draft picks—many of which were used on some of the 49ers' best defensive players of this era. Look no further than players like Patrick Willis, Ray McDonald and NaVorro Bowman as integral draft choices in the pre-Harbaugh era.
Then, one can factor in the addition of defensive end Justin Smith in 2008. Suddenly, the 49ers defense started looking legit.
Bleacher Report featured columnist Dylan DeSimone breaks this down in an excellent piece found here.
One of the first critical decisions made by the new Harbaugh regime was to bring in a talented pass-rusher.
Harbaugh and general manager Trent Baalke did just that by drafting former-Missouri standout Aldon Smith with the seventh-overall pick in the 2011 NFL draft. They also added cornerback Chris Culliver in the third round.
Almost all of the pieces were put in place. San Francisco had a plethora of talented veterans combined with a group of young players that resulted in one of the most dominant defenses in 2011.
That year, San Francisco's defense ranked second in the NFL in points allowed—averaging 14.3 points per game. The secondary produced a whopping 23 interceptions that year and boasted 42 sacks.
In 2012, the 49ers balked in what proved to be one of their poorer draft classes in recent memory. Baalke elected to focus primarily on the offense—looking to improve in an area that San Francisco needed help.
As a result, the 49ers spent four of their seven draft picks on the offense with all three of their defensive picks coming in rounds five through seven.
Still, the 49ers defense did not need a lot of help and continued their trend of being one of the more dominant groups in the league—again ranking second in the league in points allowed.
2013 NFL Draft and Offseason
Unlike 2012, which saw San Francisco focus primarily on the offensive side of the ball, the 49ers elected to provide depth and reinforcements to the defense.
One of the highlights of the 49ers' 2013 draft class was LSU safety Eric Reid whom the 49ers moved up in the first round to draft him with the 18th-overall pick. Reid was set to replace Pro Bowl safety Dashon Goldson who left the team via free agency.
Reid highlighted a draft class that also included defensive standouts like Cornellius Carradine, Corey Lemonier and Quinton Dial.
Almost all of these signings made sense. Reid would replace Goldson. Carradine and Lemonier would provide pass-rushing capabilities—a team can never have too many pass-rushers—along with depth to incumbent starters like Aldon Smith, Justin Smith and McDonald.
The team also made notable acquisitions of players like linebacker Dan Skuta and defensive tackle Glenn Dorsey.
2013 Regular Season
If any adjective could be used to describe the 49ers' fortunes during the first half of the 2013 season, the word "turbulent" probably fits best.
San Francisco's depth chart defensively was packed. In addition to the previously mentioned draft picks and signings, the team also added cornerbacks Nnamdi Asomugha and Eric Wright.
At the outset however, San Francisco's defense experienced some early setbacks that they would have to overcome. First, the 49ers lost Culliver to a season-ending injury. Wright initially failed his physical which nullified a potential trade, yet the 49ers were able to sign him outright after he was released from the Tampa Bay Buccaneers.
After winding up on the non-football injury (NFI) list, Wright would not be eligible to play until the middle of the season.
The same went for players like Carradine and Dial—both of whom were recovering from collegiate injuries.
All of that would have been fine given the nature of San Francisco's incumbent defenders. Yet, the injury bug took its toll early and often for the 49ers.
This is where we can see the value of San Francisco's depth.
In Week 2 against the Seattle Seahawks, starting defensive tackle Ian Williams suffered a broken ankle which cost him the season.
In stepped Glenn Dorsey.
Aldon Smith then ran into some legal troubles after Week 2 which resulted in him taking a personal leave-of-absence to address his off-the-field issues.
In stepped players like Skuta and Lemonier.
Perennial Pro Bowler Willis also missed two games due to a groin injury.
In stepped Michael Wilhoite, and the 49ers also got stellar play from Bowman in Willis' absence.
Plenty of other 49ers have been banged up over the course of this season. Justin Smith, McDonald, Dorsey and cornerback Tarell Brown have all found themselves on San Francisco's injury list over the course of this season.
Still, other players have stepped up in their absence.
Despite the seemingly endless amount of attrition the 49ers have encountered on their defense in 2013, San Francisco can still boast the 4th-best defense in the NFL regarding points allowed.
While the 49ers’ run defense ranks 12th, their pass defense ranks 10th with 2,200 yards allowed.
San Francisco has not necessarily been generating the same amount of turnovers it once enjoyed in 2011—24 thus far in 2013 compared to a season total of 47 in 2011—the 49ers are excelling in other areas.
Harbaugh described this by comparing it to an "olive jar" via Taylor Price of 49ers.com:
We've been kind of down on getting turnovers and sometimes things just kind of start breaking right for you. Kind of like the olive jar. Everybody’s familiar with the olive jar. Well, you open it up and a brand new can of olives and turn it over and no olives come out. They’re packed in there so darn tight, but if you just get one to come out, just pluck one out of there and then they want to come out, they’re just flying out of the jar. So, hopefully that’s the case for us defensively.
Olives aside, the 49ers are doing what they need to do on defense. Defensive coordinator Vic Fangio does not draw up a lot of blitzes. He does not have to.
San Francisco has been able to generate enough of a pass rush to force opposing quarterbacks to have off games. The 49ers have allowed 300-plus yards passing in only one game this season—Week 1 versus Green Bay—and even limited Saints quarterback Drew Brees and New Orleans' prolific pass attack to 295 yards in their Week 11 loss.
Despite the ineptitude from their offense this season, the 49ers defense has kept them in every game thus far this season—including San Francisco's ugly Week 2 loss in Seattle.
Unless things change drastically for the offense, the 49ers defense will likely have to play just as critical of a role if San Francisco hopes to make the playoffs this season.
With that in mind, there are a number of X-factors that come into play.
One of those players is defensive tackle Tony Jerod-Eddie.
Jerod-Eddie has filled in nicely for players like Dorsey and McDonald and showcases the versatility to line up either at the nose-tackle position or at defensive end.
In addition, the 49ers can count on getting defensive reinforcements in coming weeks. Players like Carradine and Dial have yet to make a significant impact at the NFL level—Dial in limited action and Carradine is yet to take the field.
Another variable that has shown worth is the play of cornerback Tramaine Brock who has 15 tackles and four interceptions this season so far. Brock's stellar play resulted in the 49ers waiving Asomugha earlier this season.
With veteran corner Brown a pending free agent after 2013, Brock may be the player who helps alleviate Brown's potential departure.
Brown, who left the 49ers' Week 11 game against New Orleans with a rib injury, will likely be spelled by Brock per Matt Maiocco of CSN Bay Area. The increased role may give the 49ers a better indication regarding what to do with Brown after this season.
What about those potential departures?
Along with Brown, the 49ers could potentially lose Pro Bowl safety Donte Whitner, Brock and Wright—all of whom are set to be free agents at season's end.
Whitner and Brown will probably command plenty of money in the offseason and it is yet to be determined whether or not San Francisco elects to retain them.
Brock would be a cheaper option and it is reasonable to assume the 49ers target him early for a new contract.
With Wright, San Francisco is probably still in a "wait and see" mode.
The 49ers also have to consider future contracts for players like Aldon Smith and Chris Culliver—both of whom, among others, will be free agents after the 2014 season.
Here is where depth makes sense. San Francisco has built incredible depth through trades, free agent acquisitions and the draft.
It has helped thus far and should continue to do so in the future.
In all likelihood, the 49ers will probably spend a considerable amount of their 2014 picks upgrading the offense—possibly in the wide receiver category. Yet the 49ers may also elect to bolster their defense again, especially in the secondary where they should plan to lose at least two starters—Brown and Whitner.
That question remains to be answered.
In the meantime, the 49ers have enjoyed the depth on their defense. Given how much this unit has factored into San Francisco's 2013 season, the 49ers can ill-afford to run thin defensively.
Fortunately, that has not been the case.
San Francisco's defense is the primary reason the team still has a winning record. The unit has suffered its fair share of injuries which have hampered—although not ruined—the 49ers' chances of returning to the playoffs in 2013.
While there remain plenty of question on the offensive side of the ball, the defense has stood firm and kept this team in games over the course of this season.
They will need to continue doing so.
Thankfully enough, the 49ers are deep on defense. They have gotten stellar play from backups when needed. They have executed well enough to remain in the conversation for top NFL defenses.
That is a good sign moving forward and something 49ers fans can still boast about even if the team as a whole is struggling.
Peter Panacy is a featured columnist for Bleacher Report, covering the San Francisco 49ers. Follow him @PeterMcShots on Twitter.