Most modern National Football League defensive formations use four defensive backs (two safeties and two corners); Canadian Football League defenses generally use five defensive backs (one safety, two defensive halfbacks, and two corners). A cornerback's responsibilities vary depending on how the defense assigns protection to its defensive secondary. In terms of defending the run, often corners may be assigned to blitz depending on the coaching decisions in a game. In terms of defending passing plays, a corner will be typically assigned to either zone or man-to-man coverage.