The NFL informed teams on Saturday that training camps will open on time even though discussions with the players' union regarding testing for the coronavirus and other health and safety protocols are ongoing.
Rookies for Houston and Kansas City are set to report Monday and rookies for other teams are due on Tuesday.
Players for all teams are scheduled to report by July 28.
Many prominent players expressed their thoughts in a social media blitz Sunday.
''We need Football! We need sports! We need hope!'' Saints quarterback Drew Brees wrote on Twitter.
''The NFL's unwillingness to follow the recommendations of their own medical experts will prevent that.
If the NFL doesn't do their part to keep players healthy there is no football in 2020. It's that simple. Get it done (at)NFL.''
Seahawks quarterback Russell Wilson said he is concerned because his wife, Ciara, is pregnant.
He wrote: ''My wife is pregnant. (at)NFL Training camp is about to start.. And there's still No Clear Plan on Player Health & Family Safety. ????
We want to play football but we also want to protect our loved ones. (hashtag)WeWantToPlay.''
NFL Players Association executive director DeMaurice Smith and President JC Tretter addressed the union's concerns in a 90-minute videoconference call with reporters last Friday.
Under the collective bargaining agreement, the NFL has the right to impose report dates and teams can fine players who don't report.
The NFLPA could file a grievance to argue the league isn't providing a safe work environment under the labor deal.
with files from AP-Sports