There is actually about a 2% cushion of minutes for each player before you will see any fatigue number change at all. On top of that, you will not see a change in overall performance for just a % or 2, so you can play at basically 100% down to around 18,900. However, when using less than "full" minutes, any early season OTs can really kill you for a while. It's a calculated gamble, that can pay off, if you're smart about it, get a bit lucky, and manage the minutes carefully.