On passing plays, the offense always has at least five people blocking. From the quarterback's left to right, they are the left tackle, left guard, center, right guard, right tackle (known collectively as the
offensive line). The quarterback will throw the pass, and is not an available blocker. Any other player is available to block, or to be a target for a pass, depending on the play design and modification by the quarterback and center based on what they see the defense doing. By nature, blitzes are risky endeavors for the defense. Since the defense is taking away coverage defenders to rush the quarterback, this usually means that the
secondary can not afford to miss any coverage assignments. The defense does not and cannot cover all offensive players, but rather through the blitz, is proactively involved in pressuring the quarterback—specifically, trying to
sack them, throw off their timing, or force them to make an error such as an
interception or
fumble. The most common blitzes are linebacker blitzes. Less common is sending a defensive back on a blitz, whether safety blitzes in which a
safety (usually the free safety) is sent, or corner blitzes where a
cornerback is sent. Sending a defensive back on a blitz is even riskier than a linebacker blitz as it removes a primary pass defender from the coverage scheme. Despite this, the pressure is very severe because a blitz by a defensive back is usually not anticipated by the offensive team's blockers. A blitz is not needed if the front four players on defense can generate sufficient pressure. ==Defensive shells and techniques==