How similar are plays from team to team? Say you've been playing as a defender (if that's the right term) for the Miami Dolphins, would it be that different if you moved to New York?
Depends on the coach. Some run simple offenses/defenses, and others run incredibly unique and complex ones. There are of course a group of core-plays that all teams will have in their playbook, and there are several distinct types of formations. 3-4 defense, 4-3 defense, spread offense, etc. If you have someone like a Rex Ryan running your defense (New York) or Sean Peyton running your offense, you're going to have a lot to learn.
The biggest problem is learning the terminology and nuance of each team. You might have an identical formation to a previous team/coach, but depending on what the other team is doing, be expected to make different adjustments. And that's assuming you read the other team correctly. Even if 1 person messes up a read for something like a block, the play is almost certain to be over since the QB will get sacked in seconds. If you're a corner or linebacker and you blow a coverage, it could be a wide open TD pass. There's also the "type" of personnel that you specialize in. To use your example,
a linebacker that excels in coverage and chasing the ball moving from Miami will be blitzing much more often in NY (Jets). They'll have to retrain themselves to think a certain way in their position and be expected to react in a way that the scheme calls for.
A lot of kids coming from college aren't used to running books as complex as those found in the NFL, so it's the biggest set back for them. Since players study opposing teams every week before playing them, veterans are more familiar with other teams and packages to begin with.
