Remix 6 said:
and also doesnt the 3-4 rely on speed of the LBs?
No, the Tampa-two defense relies on speed at LB.
The 3-4 relies upon versatility at LB.
A 4-3 linebacker can be light if he is fast.
A 3-4 linebacker has to be able to do three things well - rush the passer, string out and tackler the runner, and cover receivers - tight ends, wide receivers, or backs.
You will see plenty of plays where McGinest would drop into coverage on a slot guy, and someone else rushes. Vrabel as well. Remember the killer chuck he put on the tight end near the end of the St Louis Super Bowl?
Roman Phifer was a pass coverage specialist at ILB, usually covering tight ends but also backs and sometimes receivers. Ted Johnson was notable for dropping into coverage when quarterbacks threw over him - he was a bit more one-dimensional as a run-stuffer at ILB.
At the same time, a 3-4 OLB needs to be able to function as a DE, drop his hand, and explode into the backfield over the tight end. Then the ILB on his usually moves into an OLB role. Thus the value of a guy like Bruschi, who can play OLB, on the inside. Beisel is another guy who can play either position - not particularly well in the first eight games in the Belichick 3-4 - and can operate as an OLB when the OLB on his side switches to DE.
The nice thing about the 3-4 and picking up players is that you don't need the fastest linebackers. A guy like Ray Lewis at ILB wouldn't really work that well here. Cato June certainly wouldn't. The league values speed, so the Patriots are able to pick up versatile guys a little cheaper.
That said, the reason they haven't drafted many linebackers is that the college system doesn't generate many that fit the Patriots needs - big and versatile. This draft is very different, and has many linebackers or DE's that could fit their system.
Greenway, who many people are interested in, would likely transition into an ILB role in this system. Spencer Havner would as well. Mike Kudla, a college DE, would project to an ILB in this system.
There are at least eight college DE's who project to 3-4 DE's in the Patriots system, such as Lawson, Wimbley, Anderson, Guillory, Gocong, and so forth.
But, back to the original question, Belichick's system is based on versatility. He is a game-planner, and always has been. He spends the time breaking down tape to evaluate a team, and likes to take away what they most like to do. That requires changing the defense week to week.
Many coaches prefer to develop a system that simplifies the scheme for the players, so through repetition, coaching, and selection they become excellent at their specific role and technique. Miami under Wandstedt used this approach.
Belichick is the opposite. The three game series against Indy-Pittsburgh-Philly in playoffs last year demonstrated this. Against Indy, they played a deep zone, dropping everyone, and played a pounding ball-control offense. Against Pittsburgh, they played an aggressive attacking defense and threw over the top of the Pittsburgh defense, attacking their safeties. Against Philly, they played a 2-5 defense, setting the edges and keeping McNabb and Westbrook contained in the backfield.
Thus, the 3-4 offers much greater versatility, which fits Belichick's approach. The players that were here when he arrived were irrelevant to his decision.
People sometimes point to Greg Spires as the only player Belichick released from the Patriots who has been more successful elsewhere -- and thus a mistake in releasing him. But he is a perfect fit in the Tampa-two system as a defensive end, and was not agile or versatile enough to play OLB in the Belichick 3-4. He won a Super Bowl ring as a starter with Tampa Bay, but would have been a special teamer on the Patriots.
