Defensive Pairings

When we, or anyone, speaks of defensive pairings, what are we really talking about? Here is a breakdown of what I believe defensive pairings to mean. There are weak pairings and strong pairings, so for the sake of this explanation, we will assume average for each level.
Top Pairing – These are the teams best defenders. Norris trophy candidates and top quality, versatile defensive players that can do more then just defend well. They have to be able to play a lot of minutes without showing too many weaknesses.
2/3 Defender – These are the tweeners, able to play top minutes but shouldn’t for too long of stretches as their weaknesses will become more apparent, or able to compliment the other top pairing well. Marc Methot is a good example of the latter.
Second Pairing – Quality defenders who can play a lot of minutes, but are just a bit below the top pairing caliber of skills. More weaknesses, but still a lot of skill.
4/5 Defender – These are the tweeners that are good defensemen, but should not be given too many second pairing minutes as they may be slower or have more glaring holes in their game.
Third Pairing – These are the guys that let the top 2 pairings have a rest. They eat up some minutes while trying to shutdown the other team. Usually called the shutdown defenders, sometimes called depth defensemen. They may also be PK or PP specialists. Joe Corvo is a good example of the latter.
6/7 Defender – True depth defenseman. In and out of the lineup as needed. Not quite good enough for a regular role.
7/8 Defender – Good AHL defender that just can’t get into NHL games without an injury.