There is no doubt some of these guys have world class speed and some are A-level athletes. But there are several questions
1. How many NFL players possess that speed?
2. Does world class speed alone make you an A-level athlete if you don't have other attributes? Like strength, stamina, reflex, coordination.
3. Are obese NFL players who are basically there to provide pounds of flesh for the human shield also A level athletes?
4. Does having world class speed and skills for an NFL player translate into MMA, other combat sport or any other sport? We had Ochocinco try out soccer in MLS (which is low level soccer league by the world standards). He failed miserably, because in soccer and MMA for that matter you need a lot more advanced technical skills and tactical IQ, the technical and tactical skills are completely different.
I think you need to train a sport from a young age to achieve a world class level. Most European soccer teams have their own youth development academies. They usually take in kids as young as 5 years old and stop taking in kids that are older than 11. Reasoning behind that is that it's common knowledge, at least in soccer, that you can't train certain coordinational and technical skills if you start training after age of 11, so no point investing in those kids. That's why I think no one will be able to catch up with Khabib who started training martial arts at age of 4, at least when it comes too grappling.