After a busy off-season, Damar Hamlin is back, Odell Beckham Jr. is a Raven, Sean Payton leads the Broncos, and 10 players are out because of gambling violations.
The league and the union said the concussion protocol was followed after Dolphins quarterback Tua Tagovailoa hit his head two weeks ago. But his return to that game has prompted a change in the protocol.
Physicians assessing head injuries at N.F.L. games are expected to be able to diagnose concussions. But recent injuries to Tua Tagovailoa raised questions about how effective the doctors can be.