I am a musician. I played the cello in many orchestras and in occasional recitals. I see a similarity between orchestra, and team sports. In orchestras, all the musicians play together to make a complete sound. And yet, if one instrument is out of tune, out of time, or out of sync, the entire orchestra ensemble sounds terrible.
Ask any musician if he practices and the answer has to be the familiar one: if I miss one day, I know it; if I miss two days, the critics know it; and if I miss three days the audience knows it.
The football players have an ironclad contract that limits the amount of group practice. But, there don't appear to be any restrictions on individual practices.
For instance, musicians practice scales, arpeggios, and finger exercises. Football players should practice the equivalences: running, bench pressing, and tackling. These are the same as scale, arpeggios, and finger exercises for musicians. The more they practice, the better they will be.