49ers Blog and Q&A

The 49ers almost certainly will employ a 3-4 defense next season. That's the scheme favored by Jim Harbaugh's defensive coordinator at Stanford, Vic Fangio. It's the scheme that current defensive coordinator Greg Manusky has run in San Francisco since 2007.

The advantages of a 3-4 defenses, according to proponents, are both strategic and personnel-oriented. As opposed to a 4-3 defense, in which the pass rush comes from the two defensive ends, the 3-4 defense has more element of surprise. The primary pass rushers are the two outside linebackers. On a given play, one might rush and the other drop into coverage. On the next play the other linebacker, or both - or neither - could rush the passer. The point is that a 3-4 system gives a defensive coordinator more versatility and gives the opposing offensive coordinator more to think about. Anyone who watched Dom Capers' Green Bay defense on Sunday saw a defensive coordinator utilize the creativity inherent in a 3-4 scehem to its maximum degree.

The 3-4 also can be advantageous from a personnel standpoint. While 4-3 defensive ends come at a premium - think Mario Williams, Julius Peppers, etc. - 3-4 linebackers often can be had at little expense. They are typically undersized defensive ends in college, guys who are productive at the university level but who tend to fall down draft boards because they are not the 265- to 280-pound prototype 4-3 NFL teams are seeking. They also tend to make good special teams players, which allows them to be productive early in their careers while they are otherwise learning their new position.

But the 3-4 is only effective if a team can find the right personnel to run it. When it comes to the 49ers, for instance, the theories of the 3-4 defense haven't exactly panned out. They have drafted several college defensive ends - Manny Lawson, Parys Haralson and Jay Moore - in recent seasons but none of them have turned into much of a pass rusher.

Lawson and Haralson started every game this season at outside linebacker. Lawson is very good playing in space but struggled when rushing the passer. He had 2 ½ sacks this season. Haralson was slightly better in the sack department - he had four - but is awful when it comes to coverage and playing in space. Therefore, the two ended up having concrete roles, and the 49ers lost the element of surprise a good 3-4 defense should have.

Another component that distinguishes a 3-4 defense is the presence of a nose tackle. The 49ers' starting nose tackle, Aubrayo Franklin, will be an unrestricted free agent, as will two of the team's outside linebackers, Lawson and backup Travis LaBoy (five sacks). Which means the 49ers appear to be in a sort of no man's land when it comes to personnel and the scheme they should run.

From a personnel standpoint, it might be easier to run a 4-3. The team's sack leader this season was Justin Smith, who ended up with 8 ½ sacks. Smith is a former 4-3 defensive end in Cincinnati who will be going to his second straight Pro Bowl. The 49ers also have an abundance of players -- Ray McDonald, Isaac Sopoaga, Ricky Jean Francois, even Smith - who seem custom-made to play defensive tackle in a 4-3 scheme.

The trick would be finding more defensive ends. Ahmad Brooks fits that description at 6-3 and about 265 pounds. He's perhaps the most talented pass rusher on the team and one who distinguished himself as a scout-team defensive end when he first arrived in 2008. Brooks was relegated to being a backup outside linebacker the last two years because coaches didn't think he was well-versed enough in coverages and everything else a linebacker had to do in their scheme. At defensive end, that wouldn't be an issue.

Yes, in order to be an effective 4-3 defense, the 49ers would have to find more defensive ends - perhaps in the draft - and that's not easy to do. But to run a 3-4 defense, they'd have to re-sign Franklin and find some 3-4 outside linebackers. And they've proven that's not so easy to do, either.

-- Matt Barrows