Yesterday, commenter Slam described the Oakland Raiders’ defense as “brutal.” So brutal, in fact, Slam predicted the team would “be lucky to win 7 games this year.”

Commenter Tru, on the other hand, thought Carson Palmer would be the lynchpin of Raider success. While Palmer’s performance will be important, Slam is right: The Raiders’ success actually hinges more on the defense than on the offense.

Again, this is not say that the performance of Palmer and the rest of the offense is not important; rather, it is that the offense is a known commodity, whereas the defense is not. According to Football Outsiders, “Offense is more consistent from year to year than defense, and offensive performance is easier to project than defensive performance.” The Raiders offense, though not great, is hardly problematic.

As you can see, the Raiders offense was generally better than average, especially in close games. Though it doesn’t seem like much, a positive DVOA is essential to a playoff berth. Last season, only two playoff teams (Denver and Cincinnati) had negative offensive DVOA scores. Cincinnati’s -1.4% is somewhat misleading, though. The team finished the first nine weeks with a positive only to back-slide into the playoffs. Denver was just a statistical anomaly.

The new offensive system notwithstanding, the Raiders are in position to at least match last season’s performance, if not better it. If Austin Lee of Pro-Football Focus is correct, it’s reasonable for the Raiders to expect Palmer to maintain his current level of play. As Lee points out, “The typical franchise quarterback will produce solid numbers from ages 25 to 36.”

The defense, on the other hand, should be cause for great concern. Though the team might have actually upgraded both their defensive line and secondary, it is the linebacking corps that stands the greatest chance of being, as Slam termed it, “brutal.”

With Matt Shaughnessy returning, the Raiders can move Desmond Bryant back inside, which will provide much need rotational depth. Fifth-round pick Jack Crawford is having a stellar camp and should provide rotational depth for Lamar Houston.

At cornerback, Demarcus Van Dyke has been the surprise of camp thus far, but perhaps he shouldn’t be. In limited opportunities, Van Dyke played well last season, posting a Success Rate (The percentage of plays targeting a defensive player on which the offense did not have a successful play) of 68%. Ronald Bartell, who ranked 12th in success rate in 2010, is an obvious upgrade over both Stanford Routt and Chris Johnson—if he can return to his previous form, that is.

The Raiders failed to upgrade a linebacking corps that was one of the worst in the league last season. According to Football Outsiders, Rolando McClain “was one of the most-targeted and least-effective cover linebackers in the league” and Aaron Curry “looked good at times, but sometimes displayed the amazing lack of instincts that made him expendable in Seattle.”

Newly acquired Philip Wheeler might an upgrade over the departed Kamerion Wimbley in pass coverage, but he is not nearly as effective against the run or rushing the passer. In total, no Raiders’ linebacker ranks in the top-40 of run defenders and only Wheeler (13) ranks in the top-30 of pass defenders.

With such a glaring weakness, head coach Dennis Allen and defensive coordinator Jason Tarver will have to find ways to protect their linebackers from both the run and the pass. Of course, doing so puts added pressure on the defensive line and the secondary, pressure the two units were unable to shoulder this past season. As you can see from the following chart, the defense, save for in the red zone, was awful. (Note: the higher the DVOA on defense, the worst the unit performed).

If the coaching staff cannot find a way to scheme around the weaknesses of McClain and Curry, then the Raiders stand a good chance of repeating their 2011 performance. Given the improvements made by the rest of the division, Slam is probably right: The Raiders will likely finish below .500 for the seventh time since 2003.