I am going to outline the traditional pass blocking responsibility of a 3-4 rush line. To simplify this, I am going to limit this discussion to strongside (with the TE) and weakside (without the TE). On some occasions, the TE will go in motion. In this case, the blocking responsibilities simply switch sides. Sometimes you will see teams line up in two TE sets for blocking purposes. This provides more traditional one-on-one responsibility, but is rare.
The 3-4 OLB has significant pass rush responsibilities basically acting like a hybrid DE in 4-3 pass rush lines. They also need to be athletic enough to cover the pass. Wade Phillips has generally used the 3-4 OLB in very traditional roles. He has the "drop" (Leber) and "rush" LB (Foley).
Some general blocking principals include:
• The LT takes on the ROLB, while the LG slides over to take on the RE.
• Generally, you have the RILB act in coordination with the ROLB (rush LB) and cover the empty flat.
• The Center takes on the NT with the RG potentially helping and reading any blitz from that side.
• The RT takes on the LE.
• The TE generally goes out in pattern and the LOLB goes with him or chucks him on the line before rushing the passer.
GENERAL RUN BLOCKING
It is a little more difficult to identify the blocking schemes from a running perspective. However, both OLB have outside contain and are responsible for turning RB's into the rest of the defense. The 3-4 ILB has B gap responsibility, but the open side ILB (RILB) usually is the beneficiary, because he is generally protected by the natural flow of blocking schemes.
Shawne Merriman: ROLB
I do not view OLB as a hole on this team; however I do think the team needs to utilize the "drop" LB more as a pass rusher. Steve Foley's versatility helps this situation. He is capable of being the "drop" LB and while he was a productive rusher, he lacks the speed you want in the primary rush LB. Merriman has more explosion, burst, and speed than Foley. In my opinion, he could provide 12 to 15 sacks from the ROLB position and the Chargers could be less predictable with their "drop" and "rush" positions.
"I can run with any back or any tight end," Merriman said. "And at the same time I can go against any tackle. Whatever teams want to do with me is fine with me and I can adjust to it."
Derrick Johnson: LILB
The Chargers system is predicated by creating traffic to free up the RILB, Donnie Edwards. Against the pass, he is the primary cover LB when we rush Foley. Against the run, he is often the responsibility of the FB or a lineman who chucks a lineman and then slides down to Edwards. In many cases, Edwards does not get touched. Teams often depend on traffic to take him out of the play and he is very good at wading through that traffic.
The LILB is more of a complementary player. This player needs to be able to take on the RG and shed blocks on weakside runs. He also needs to be able to take on the FB on strongside runs when they double Jamal. Problem is that Derrick Johnson does neither of those well. He also freelances and runs around blocks, which is potentially devastating in this system creating holes the sign of craters and forcing the LE and LOLB to make plays 5 to 7 yards down the field.
"They run away from me a lot sometimes," said Johnson. "I'm probably stronger at just going and chasing the ball down sideline to sideline."
In the end, the system fits Merriman's skill set and he not only improves the rush LB position, but brings the potential versatility to expand the role of the drop LB. Johnson is not big enough or strong enough to be a hybrid DE, so OLB is out. As an ILB, his primary weaknesses are really the primary things we look for in an ILB. In the right system, Derrick Johnson is going to be a very good player. He has the potential to be a pro bowler, but this is the wrong system. It is a slam dunk for Merriman.
"I just want to be in the scheme that uses all of my physical talents," said Merriman. "The best way to help the team would be for me to use the height and the speed and the strength that I have to the benefit of the whole defense."