also: two deep · cover two
A defensive coverage with a two-high shell: two safeties share the deep part of the field, one left and one right. Cover 2 usually means zone coverage underneath; 2-man uses the same shell with man coverage underneath.
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A zone coverage in which two safeties divide the deep field in half and five defenders cover underneath. With only two defenders deep, Cover 2 can put five in the short and intermediate passing lanes. The corners also have help over the top, so they can play aggressively on the outside. The cost is the middle of the deep field: with the safeties split, the space between them is the softest part of the coverage. It is the reason Tampa 2 exists.
two deep, cover twoTampa 2, Cover 4, 2-manThe safeties still split the deep field, but the five defenders underneath play man instead of zone. It can look like Cover 2 before the snap even though the underneath assignments are different.
2-man, two man under, Cover 2 manCover 2 zoneSome staffs use Cover 2 only for the zone and call the man version 2-man. Others use Cover 2 for any coverage with two deep safeties and add another word to name the underneath coverage.