If he’s got an active infection it is probably best for him and the other people on the field if he doesn’t play.
If he’s testing negative then he should consider himself fully immune and allowed to play.
There is still open question on how long someone with an infection will spread it/shed virus. I just read a study from this summer that said it takes an average of 30 days to stop shedding. But since none of this data seems to matter to policy makers, go with the rules as they are now. No positive test, no infection, no risk. Play!
It varies a great deal. Short time if you are vaccinated. Longer if you are not.
It’s 10 days after the test for the NFL. You can’t have a fever, but you can have some other lingering symptoms as long as they are improving. Seems strange, but any shedding after 10 days is likely “dead” virus particles.
This is from SI.com:
Player with moderate symptoms passes cardiac screen (which may be conducted during 10-day isolation period subject to the Club physician’s discretion); AND
1. At least 10 days have passed since the date symptoms of COVID-19 were first reported to Club medical staff; and
2. At least 24 hours have passed since last fever without the use of fever-reducing medications; and
3. Other symptoms (e.g., cough, shortness of breath) have improved; and
4. Return approved by the Club physician, after consultation with ICS and notification of NFL Chief Medical Officer; and
5. Local regulations and requirements are satisfied.