Glossary:
Playing the ball: Just like it sounds, a defender playing the ball concentrates on the pass itself with less consideration for an individual offensive player. The benefit of playing the ball is an increased ability to intercept the pass. The downside is an increased ability to break coverage or be beat.
Playing the man: A defender playing the man focuses his attention on the receiver himself. The idea is to maintain coverage and prevent the passer from targeting the receiver.
After the jam
Jamming can be risky because a failed jam leaves the corner out of position, off-balance and a step behind. A couple years back, defensive coordinators got the wise idea to jam Terrell Owens. The ridiculously ripped Owens was more than happy to overpower opposing DBs before running past them.
Even a successful jam can backfire. A stifled wide receiver can ambush a mindless or cocksure corner unwilling or incapable of flipping his hips in an instant. Therefore, a corner must quickly transition from jamming the receiver to assuming his coverage responsibilities. Zone coverage is especially conducive to the jam, because instead of jamming, flipping their hips and running man to man with an opposing receiver, a corner playing zone must only move into his zone of control after the jam.
Zone Coverage
Zone coverage is all about quickness, awareness and reaction time. A defender playing in a zone is not stationary, but moves within that zone to the spot where he thinks he has the best ability to defend the pass. Against a single receiver, a corner working within a zone may play de facto man coverage, playing the man within his zone. More typically, zone defenders face the line and though maintaining a functional proximity to the receiver, play the ball. An offense may attempt to overwhelm a zone by sending multiple receivers into it. A defender then must make critical decisions about who he can defend, who he should defend, the range and coverage ability of other proximal zone defenders, and, sometimes, whether to concede the reception so as to limit yards after catch.
Man Coverage
Most basically, man coverage is any pass coverage in which a defender tracks one receiver throughout the play. Within that framework there are three basic types of man coverage. Two are very similar. Man-over and man-under coverage both emphasize playing the receiver close and attempting to render that receiver "covered". A covered receiver is considered too risky to throw to, both because the play may result in a pick (the downside) and because the play won’t likely result in a reception (the upside).
Man over coverage is the more conservative of the two. The defender plays "over" the receiver, that is, ahead of him or between the receiver and the end zone. This position makes it less likely that the corner will intercept the pass, but also less likely he will be beat should the receiver catch the pass. Man over is the coverage of choice when a defender lacks deep support.
Man under coverage is decidedly more risky. The defender plays "under" the receiver, that is, behind him or between receiver and the line of scrimmage. This position allows better access to the ball, but puts the corner a step behind the receiver. One of the benefits of good deep safety play is the ability to play under without risk of being burned. Paired with Deon Grant, Marcus Trufant showcased emerging ball skills without fear of being burned. Despite Russell’s nominative deep coverage, Kelly Jennings rarely played under. To be fair, Jennings has only average ball skills, but it was clear that he and perhaps the coaching staff did not entrust Jennings with the same risky under coverage.
The final type of man coverage is the rarest and most difficult. Loose man coverage involves a sort of floating zone that follows the opposing receiver. In the NFL, with the very best and most agile route runners in the world, against offenses that design picks and double moves into routes, loose zones are attempted by only the most skilled corners or against the least skilled receivers. The advantage of a loose zone is that it’s flexible and enjoys the inherent personnel advantages of man coverage: one defensive player allocated to one offensive player. For a shutdown corner, loose zone allows them to shutdown nearly an entire half of the field. Deion Sanders was the king of loose zone coverage. Sanders was famous for his ability to hide just off an opposing receiver and shoot into coverage microseconds into the pass. That ability to cover a receiver without being seen is how a corner shuts down half the field. It’s not about being everywhere; it's about maybe being anywhere. It's not about speed; it's about fear.
Tampa 2
The major difference between a typical corner and a Tampa 2 corner is the increased emphasis on run stopping and the decreased emphasis on man coverage. A Tampa 2 corner works primarily in a short zone with a deep safety shell. This allows the corner to primarily play the ball. Playing close to the line, along with the linebackers and safeties playing back, allows and necessitates the corner to be stouter against the run. A good Tampa 2 corner must be swift in the short zone, opportunistic on botched passes and able to reliably tackle in the open field.
Prototypical Jam Corner: Mel Blount
Prototypical Cover Corner: Deion Sanders
Prototypical Tampa 2 Corner: Ronde Barber