
Sorry, just stirring the ants nest for a couple of pre-season lolz.

Cool vid timmy, though for me it was choppy as hell. The Steve Matai tackle at 53 sec is awesome.
PING, as timmy said, that's Rugby (Rugby Union). There are certainly a lot of times when the ball is out and you can rest, especially when a British side is playing. In Rugby League, the ball is in play a lot more and when a tackle is made, the defending side has to get back 10 metres (approx yards) before the ball is played or they're 'offside' and can be penalised. Often you'll see the ball go from one end to the other every minute or 2.
There are 13 players on the field and 4 reserves, with a maximum of 10 changes allowed in the game, usually the same 4-6 players are rotated on and off. In Rugby Union there's 15 on the field with 7 reserves, and once you go off you can't come back on (there are some circumstances where you can).
BUT American football is a game of acceleration, power and impact, and couldn't be played that way without the Off and Def squads etc. It just wouldn't be physically possible.