Days after the NFL revealed its hopes of conducting a normal regular season and playoffs, its chief medical officer warns that nothing is a certainty during the coronavirus pandemic.

Dr. Allen Sills, a neurosurgeon who has been with the NFL since 2017, says he and other league and team medical personnel have been in constant communication with health officials throughout the country, looking at the same data they are using to make public recommendations. The NFL also has consulted with the other major sports leagues and the players' union.

"We are not doing this in isolation," Sills says. "I think the NFL is in the same place every element of society is. The hope is that soon much more widespread testing is available, which will be an essential part of restarting activities. You follow the science."

The NFL has done that in its revisions to the draft in three weeks, which will be conducted remotely with no public events. It also has temporarily barred teams from using their facilities, meeting in person with free agents and draft prospects.

Beyond the draft, the league must decide on allowing offseason workouts and minicamps that usually occur in the spring. And then on conducting training camps and the preseason.

None of that is assured.

"We have got to get a much better handle on the actual spread of this virus and how many new cases there are," Sills explains. "How it is transmitted and how we can mitigate it. We have to get to the point that when someone is tested as positive to the virus, that does not mean an immediate quarantine. If that is the case, you can't think about opening up a team sport.

"Like all other parts of society, we're trying to listen to the best advice we can. It's hard to project what will happen in a month, three months or six months No one knows. We have to do that which is not only in the best interest of the players, but league and team personnel and our fans. That is what is happening. All of our league executives have been in very regular contact with me. Every meeting starts with an update on the current medical situation."

Recognizing the stress accompanying the pandemic, the NFL and the players' union sent a letter to the 32 clubs and each player this week with suggestions on dealing with mental anguish. Among the items it addresses are loneliness; establishing a routine and sticking with it; and staying in touch with peers and loved ones while practicing social distancing.

Sills emphasizes the importance of remaining physically and mentally sharp.

"I have had regular calls with members of our medical staff and trainers and coaches and front office personnel," he says. "A lot of dialogue and questions back and forth. It is a situation where we and the players association are working hand in hand to make sure we are serving our whole NFL environment as best we can.

"That's not only about this disease but around mental health; we recognize this is a big stress for everyone. Imagine if someone had a pre-existing condition that cannot be treated. These are incredibly difficult times for people with those challenges. We have a lot of resources in these areas."

Along with his NFL duties, Sills is a professor of neurological surgery, orthopaedic surgery and rehabilitation, and the founder of the Vanderbilt Sports Concussion Center. He's been in contact with the NCAA, schools and conferences about their approaches to the coronavirus as well.

The message is the same on all fronts.

"Follow the recommendations from public health officials and infectious disease experts," he says. "We all must do that."