The cover two scheme is not new in fact it can be traced back to the Steelers teams of the 70's. It gained popularity as the most effective way to contain a West Coast Offense.
The C2 is the main counter attack for the WCO because in a true C2 defensive lineman provide all the pressure. Blitzing should be unnecessary. Defensive lineman line up "in" the gaps to slow the run, and make it more difficult for holes to open up. The main point of this form of gap control is to force the run outside to your LB's, corners, and safties.
The entire concept of the Cover 2 is to make it hard to pass on you. The name comes from the position of the safeties, who both play deep zone coverage. In this normally 4-3 coverage scheme (the Rams run it often out of their nickel package), your safeties play further back, while your linebackers and cornerbacks play zone coverage underneath the safeties. Each person underneath covers about 1/5th the width of the field for about 7 yards deep. The two safeties split the field and each cover half against the deep pass.
There are a few weaknesses to the Cover 2. All zone coverage has holes in it, and teams that run the Cover 2 are heavily exposed to deep post patterns, seam routes, medium range hooks, flooding the zone. Because of how much ground the safety has to cover, deep passes can easily overload his zone. A common play that teams run to stop it is a quick fly or out to the far sides. Once the receiver breaks the zone where the corner plays, heÃ¢â‚¬â„¢ll be in a soft zone. Realistically, itÃ¢â‚¬â„¢s about 8 yards for him to run, while the safety might have to cover 20 yards to run over there and provide help over the top. Its also a mismatch as most safeties in the NFL can not cover a receiver effectively.
The Tampa 2 is a coverage scheme out of the 4-3 that was pioneered by (now Indianapolis head coach) Tony Dungy. Its emphasis is on speed and a quick pass-rush. While the normal Cover 2 has each Linebacker or Cornerback covering about 1/5th the width of the safeties, who each cover half, the Tampa 2 pulls the middle linebacker into deep zone coverage as well, similiar to a Cover 3. What this does is allows the safeties to have to cover less ground, so they can cover the traditional soft zone past the corners more effectively. Since the middle linebacker drops into coverage to watch the center of the field, the four men underneath each cover about 25% the width of the field each. Speed at linebacker is so important here because they need to cover more ground than linebackers are normally used to covering.
What generally hurts DungyÃ¢â‚¬â„¢s system is its emphasis on speed. Faster is always better because his system is based entirely around the pass. The speed works well for passing and outside runs where the linebackers and corners can quickly converge on the runner. However, the Tampa 2 suffers from power runners. Big, bruising running backs can normally run over the smaller linebackers and a lot of times wonÃ¢â‚¬â„¢t be stopped until they reach the safety. A good running game cheats the safety out of the coverage he wants to run and makes him hesitate since he has to watch the run. When play-action passes can get involved and the safety has to respect the teamÃ¢â‚¬â„¢s running game, a lot of times it can spell a long completion or a touchdown. The Panthers are good at demonstrating this and exposing it, since they possess a power-running, play-action pass offense. A vast majority of their passes come off the play-action, and when the safety has to watch out for the run, it really opens up holes in the coverage.
Take it for what it is worth. I'm not a big fan of cover 2, if we do run it on our team then we need a major upgrade at LB. I love to watch the line though and cover two will definately make it interesting with stunts and dropping a lineman into coverage to bring a LB in......