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In American football, the 3–4 defense is a defensive alignment consisting of three down linemen and four linebackers. The 3–4 defense incorporates three defensive linemen - two defensive ends and one nose tackle, who line up opposite the other team's offensive line. Those three players are responsible for engaging the other team's offensive line, allowing the four linebackers to either rush the quarterback or drop back into coverage, depending on the situation. While the role of the defensive linemen is fairly consistent, the linebackers allow for the flexibility and versatility of the 3-4 scheme, and give defensive coaches nearly limitless options to confuse the other team's players and coaches. Depending on the situation, any number of linebackers can blitz, fake a blitz, "spy" the quarterback or runningback, or cover receivers. In key situations, a rush linebacker may be sent to cover the flat on the opposite side of the blitzing defensive back; this is called a "zone blitz". After becoming the predominant defensive alignment in the late 1970s-early 1980s, the 3–4 defense declined in popularity over the next two decades, but experienced a resurgence in the 2000s among both professional and college football teams. As of 2015, NFL teams that regularly incorporate the 3–4 defensive alignment scheme as a base include the Cleveland Browns, San Diego Chargers, Green Bay Packers, Baltimore Ravens, Arizona Cardinals, Indianapolis Colts, Kansas City Chiefs, New York Jets, San Francisco 49ers, Pittsburgh Steelers, Washington Redskins, Denver Broncos, Philadelphia Eagles, Tennessee Titans, Houston Texans, and the Chicago Bears, who will be the last team to use the defense on a regular basis. The New England Patriots returned to a 4–3 defensive front at the end of the 2011 season. The Buffalo Bills returned to a 4-3 base defense in 2014 and will continue to use the 4-3 with the hiring of head coach Rex Ryan and defensive coordinator Dennis Thurman, who was Ryan's defensive coordinator while with the New York Jets. The Pittsburgh Steelers have used the 3–4 as their base defense since 1982, the season after Hall of Fame defensive tackle Joe Greene and end L. C. Greenwood retired. In fact, the Steelers were the only NFL team to use the 3–4 defense during the 2001 NFL season, but finished the season as the number one defense in the NFL.〔http://www.nfl.com/stats/categorystats?tabSeq=2&defensiveStatisticCategory=GAME_STATS&conference=ALL&role=OPP&season=2001&seasonType=REG&d-447263-s=TOTAL_YARDS_GAME_AVG&d-447263-o=1&d-447263-n=1〕 It is believed that the Steelers success with the 3–4 defense is the primary reason why many NFL teams have started returning to the formation.〔http://www.nfl.com/combine/story?id=09000d5d80edccdd&template=without-video-with-comments&confirm=true〕 The 3–4 defense was originally devised by Bud Wilkinson at the University of Oklahoma in the 1940s. Chuck Fairbanks learned the defense from Wilkinson and is credited with importing it to the NFL.〔http://tarheelblue.cstv.com/sports/m-footbl/spec-rel/101708aab.html〕 The 1972 Miami Dolphins were the first team to win a Super Bowl with the 3–4 defense, going undefeated and using number 53, Bob Mathison as a down lineman or rushing linebacker. When the Oakland Raiders defeated the Philadelphia Eagles in Super Bowl XV, it marked the first Super Bowl in which both teams used the 3–4 as their base defense. Also notable, the Big Blue Wrecking Crew, the defensive unit for the 1986 New York Giants who won Super Bowl XXI, was a 3–4 defense and featured all-time great Lawrence Taylor as outside linebacker. By the mid-1990s, only a few teams used a 3–4 defense, most notably the Buffalo Bills and Pittsburgh Steelers. ==Defensive line== The defensive line is made up of a ''nose tackle'' (NT) and two ''defensive ends'' (DEs). Linemen in 3–4 schemes tend to be larger than their 4–3 counterparts to take up more space and guard more territory along the defensive front. As a consequence, many 3–4 defensive linemen begin their NFL careers as 4-3 defensive tackles, as younger players typically do not possess the size, weight, and strength to play on a 3-4 defensive front. They must be strong at the point of attack and are aligned in most cases head-up on an offensive tackle. First and foremost, they must control run gaps. Size and strength become more of a factor for linemen in 3–4 defenses than in 4–3 defenses because they move primarily within the confines of line play and seldom are in space using athletic ability. Ideally 3–4 DEs should weigh and be able to beat double teams by getting a push. The 3–4 nose tackle is considered the most physically demanding position in football. His primary responsibility is to control the "A" gaps, the two openings between the center and guards, and not get pushed back into his linebackers. If a running play comes through one of those gaps, he must make the tackle or control what is called the "jump-through"—the guard or center who is trying to get out to the linebackers. The ideal nose tackle has to be much bigger than 4–3 DTs, weighing around 335 pounds or more. An AFC Personnel director used Ted Washington as an example of an ideal nose tackle: "In his prime, Ted Washington was the ideal guy. He was huge, had long arms, and you couldn't budge him. He could hold off a 320-pound lineman with one hand and make the tackle with the other."〔 The base position of NT is across from the opposing team's center. This location is usually referred to as ''zero technique''. The two DEs flank the NT and line up off the offensive guards. The location off the offensive guard is usually referred to as ''three technique''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「3–4 defense」の詳細全文を読む スポンサード リンク
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