During Tuesday's Vic Fangio Watch post, some discussion developed over whether the 49ers should switch back to a 4-3 defense and abandon their attempts at the 3-4. Additionally, I made some comments in our previous post today about the 49ers pass rush abilities and personnel needs. Such needs would be significantly affected by a switch back to a 4-3 defense.

After the jump I've posted a basic rundown of the 49ers by position along the front seven. In a potential switch to the 4-3 the 49ers have a good deal of options, but also some potential holes and general question marks. the first such question is in the form of nose tackle Aubrayo Franklin. The general outlook right now is that  Franklin will be back next year under the franchise tag. This is of course assuming the franchise tag survives into the eventual new CBA.

If he comes back in the 3-4, he locks in at nose tackle and that's that. If the team goes to a 4-3, one has to consider whether Ricky Jean-Francois and Isaac Sopoaga could be adequate options at the second defensive tackle position. In the 4-3 it becomes more than just occupying offensive linemen to open holes for the linebackers. The defense would need serious playmakers along the four man front. At this point there are a lot of question marks in there.

If the team made the switch to a 4-3 I would suspect Takeo Spikes would not be back in 2011. Patrick Willis would occupy the middle linebacker spot and the team would have a host of options at outside linebacker. If the team brought back Manny Lawson, I'd imagine he'd fill a similar role to what Julian Peterson occupied when he was in San Francisco's old 4-3. He could bring the pass rush or defend against tight ends and running backs.

If that were the case, the team would suddenly have an over-abundance of linebackers. You'd have Parys Haralson, Ahmad Brooks, NaVorro Bowman, Scott McKillop, and Thaddeus Gibson available in some form or fashion. McKillop likely slots in at special teams in a Jeff Ulbrich role, while Gibson will be battling for any roster spot he can get. However, that leaves three linebackers in Haralson, Brooks, and Bowman. Would the 49ers be best suited re-signing Lawson and then dealing either Haralson or Brooks once trades can happen? Or do they keep all of them for the depth?

The stories around the Internet seem to think it's more or less inevitable that Vic Fangio ends up as the 49ers defensive coordinator. If that's the case, it appear as though we'll see more 3-4 than 4-3 in 2011, in which case much of this argument is moot. Nonetheless, it's of some value to consider. Before we continue on with further defensive discussion, what kind of defense would best suit the 49ers in 2011? This is based in large part on the current roster, but feel free to factor in free agents and the draft.

Defensive Tackles
Ricky Jean-Francois
Isaac Sopoaga
Aubrayo Franklin (UFA)

Defensive Ends
Justin Smith
Ray McDonald
Isaac Sopoaga (obviously an inside option as well)
Demetric Evans (UFA)
Will Tukuafu

Linebackers
Patrick Willis
Ahmad Brooks
Parys Haralson
NaVorro Bowman
Scott McKillop
Thaddeus Gibson
Manny Lawson (UFA)
Takeo Spikes (UFA)
Travis LaBoy (UFA)