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Listening to one of today's linemen discuss his duties is a little like listening to a physicist describe some new process for detecting subatomic particles. "Our defense basically revolves around the concept of playing keys," says Tackle Henry Jordan, who together with Ends Willie Davis and Lionel Aldridge and Tackle Ron Kostelnik forms the front four of the Green Bay Packers. "We move with them all the time. On a trap play, for example, Aldridge's opposing tackle will fake a pass block by going for our middle linebacker. Now I've moved with my key, the offensive guard, so I'm trapped by him. Then Aldridge will move with his key when he sees him going for the linebacker. If Lionel had simply crashed straight ahead, he would have been trapped by the guard who has pulled and come across. But instead he has moved into the hole by following the tackle, and thus has fouled up the trap."
Haunches & Knuckles. It sounds like utter gobbledygook until Jordan explains what he means by "playing keys." In simplest terms it means to study an opponent, searching for clues to his intentions, then outmaneuvering him to break up the play. It can be as simple as noting the direction of an enemy lineman's charge—and divining that the play will go the opposite way. It can also be pretty cute. "When an offensive guard comes up to the line," says Tackle Ray Jacobs of the American Football League's Miami Dolphins, "I watch the way he sets himself. Some guys lean back on their haunches, which means that they're either going to pull for a run or go back for a pass protection." Tackle Alex Karras of the N.F.L.'s Detroit Lions examines opponents' knuckles. If the knuckles are white, they intend to block forward and the play is a run; if the knuckles are pink, the play is probably a pass.
Once he reads his key and analyzes the play, the defensive lineman reacts —and reacts fast, trying to beat his opponent to the block, catch him off-balance, squirt past him before he can plant himself. To confuse blockers, defenders will "stunt," or loop around each other; they may charge high to hurdle a block, or duck low to "submarine" under. They clutch at shoulder pads and jerseys, trying to spin blockers aside and clear a path to the ballcarrier. They have, in fact, become so adept at slipping blocks that not even the punter, standing 15 yds. back of the line of scrimmage, is safe any more. Kickers who used to count on 1.5 sec. to get the ball away now find that they must boot it within 1.2 sec.; this season in the N.F.L., no fewer than ten punts and 28 field-goal attempts have been deflected by onrushing defenders.
If a defensive lineman can't beat a blocker with finesse, there is always brutality. A favorite trick is the "vacuum pop"—clapping his hands over the earholes of an offensive player's helmet. Another is the karate chop, delivered with a beefy forearm encased in layers of tape. "You try not to let it get too personal," says Defensive End Sam Williams of the Atlanta Falcons. "But what the up-front struggle really amounts to is an angry, private little war between two people."