As someone who follows the NFL and NBA, my issue with the playoff system is that you have teams losing on purpose to get an easier 1st round playoff draw. Imagine if the PL had it, if we won the final game of the season, we'd draw Citeh away, but if we lost, we'd get Everton at home. It makes no sense to win that final game, and that's the issue with playoffs, the system is flawed.
I follow NFL and I don't believe I've ever know a team to throw the last game of the season to benefit from a better play off position.
You will be aware the NFL introduced inter-divisional games for week 17 of the regular season to counter that very concern, but I believe it was a pro-active move rather than a reactive one.
Aside from anything else, NFL is such a physical game you can't go into any tackle at less than 100% or you come off second best every time, and the roster system doesn't allow for you to play an entire team of reserves.