Building muscle and possessing the athletic ability to play in the nfl are disparate genetic qualities.
You may possess muscle to be explosive, strong, fast. But that doesn't necessarily mean you can build muscle better than someone who is genetically inclined to do so.
Ramy has interesting genetics when it comes to accruing sheer muscular weight, but the guy can probably barely walk. Huge amounts of muscle is not equivalent to having muscular and cardiovascular functionality.