With its 2021 season at hand, there are many promising signs for the NFL. About 93 percent of players and more than 99 percent of coaches and team staffers are vaccinated. Ticket sales are strong. The league is pressing forward with plans for a complete season played in full stadiums, with a 17th game for each team and a prosperous economic outlook bolstered by new broadcasting deals and recently forged sports-betting partnerships.

But if all was supposed to be well and everything practically normal for what would amount to a post-pandemic season, the league is not there. Not yet, at least.

“Our challenge right now … is certainly that we are in a major surge,” Allen Sills, the NFL’s chief medical officer, said recently. “It’s no secret to any of you, nor is it a secret to any of us in medicine, with the impact that the delta variant is having.”

The coronavirus is not the nonissue that the NFL — and the country — hoped it would be by this fall. The league and teams continue to deal with significant virus-related challenges before the season kicks off Thursday night in Tampa. The Dallas Cowboys are expected to be without six-time Pro Bowl guard Zack Martin in the opening game against the Buccaneers after he tested positive for the virus, Coach Mike McCarthy said Sunday.

The league said late last month that it is interested in a vaccine requirement for all players, but the NFL Players Association has not consented to that. The NFL did mandate vaccinations for coaches and team staff members for them to be permitted to continue to work closely with players.

Even without a mandate for players, Sills called the NFL’s vaccination rate “remarkable.” He said teams’ facilities are “the safest places” in their communities and added, “If we had those kind of vaccination rates in society right now, we would be in a far, far different place with regard to where this pandemic currently is.”

Yet pockets of vaccine wariness remain in the NFL.

“It’s a personal decision for me and my family,” Indianapolis Colts quarterback Carson Wentz said at a news conference last week. “I respect everybody else’s decision, and I just ask that everybody does the same for me. I know that’s not the world we live in. Not everyone is going to equally view things the same. But, yeah, no one really knows what’s going on in someone else’s household and how things are being handled.”

The NFL focused on education and incentives for players to be vaccinated. Under the protocols developed by the league and the NFLPA, unvaccinated players remain subject to the daily coronavirus testing that was in effect last season. They face five-day quarantines if they’re identified as high-risk close contacts to an individual who tests positive. Vaccinated players and staffers, meanwhile, are exempt from contact-tracing quarantines and will be tested on a weekly basis during the season, up from once every two weeks during training camp and the preseason.

“There’s consequences with not being vaccinated,” Colts General Manager Chris Ballard said. “... Do I think everybody should be vaccinated? Absolutely, I do.”

The health ramifications are clear. Sills said that during the first three weeks of August, unvaccinated players leaguewide tested positive for the virus at a rate seven times higher than that for vaccinated players.

There also are competitive implications for teams and players, given the increased likelihood of unvaccinated players being unavailable because of positive tests or contact-tracing quarantines. The NFL told teams that they could face forfeits if any games cannot be played because of an outbreak caused by unvaccinated players or staffers and cannot be rescheduled.

“Hey, look, I could beat my head against the wall,” Ballard said. “I could go in there and raise all kinds of hell and go off. [But] that’s just not how we roll, man. I believe in our guys. I believe in what they stand for, and I’ll stand by them. We’ll continue to work on the vaccinations. It’s not like we’re done. It’s not like we’re done educating.”

The competitive hazards are particularly high for teams with unvaccinated quarterbacks. Wentz and Minnesota Vikings starter Kirk Cousins were among the players to quarantine during training camp and the preseason. Lamar Jackson, the 2019 league MVP for the Baltimore Ravens, tested positive for the virus for the second time in eight months, then said upon rejoining the team that he remained uncertain about being vaccinated. Cam Newton missed practice time with the New England Patriots because of what the team called a misunderstanding about the protocols, resulting in Newton being subjected to a five-day reentry process that does not apply to vaccinated players.

The Patriots released Newton last week, going with rookie Mac Jones as their starting quarterback. Coach Bill Belichick said Newton’s vaccination status was not a factor in the move.

“The number of players and coaches and staff members that have been infected by covid in this training camp who have been vaccinated is a pretty high number,” Belichick said. “So I wouldn’t lose sight of that.”

But Belichick had acknowledged when Newton was out that Newton’s absence from practice represented an opportunity for Jones.

“I do feel we’re in a much better place than we were last year at this time,” Sills said. “I make that statement because I think we have a much more complete understanding of this virus and its transmission and the testing and identification of it. We also have a lot of experience with protocols and mitigation measures which have worked and have been successful. But by far, the main driver of my optimism is that we have a very highly effective set of vaccines.”

Sills said he has told teams that the NFL “will see positive tests in vaccinated people.” But the league’s experience so far, Sills said, is that those cases involve “very mild illness … and also shorter duration of illness.” Sills said the NFL has seen some clusters of cases on teams but nothing that he would term an outbreak. The difference, he said, is that an outbreak would include evidence of ongoing and widespread transmission of the virus within a team.

One of the clusters involved players and coaches on the Tennessee Titans after they were in Tampa for joint practices with the Buccaneers.

“I went to dinner when I was in Tampa … and I felt safer because I was vaccinated,” Titans General Manager Jon Robinson said at a news conference soon after. “I felt like I could go eat a meal. … If you do contract it and you’re vaccinated, it looks like the science has shown that you’re sick for a day or two and then you’re going to get through that. So there’s comfort in going out to dinner and trying to get back to some degree of normalcy, which we all want to do.”

The ongoing issues for the NFL, Robinson said, are reflective of what’s happening in the rest of society.

“My sister is a schoolteacher … and she said it’s rampant in their school, and they’re doing everything they can,” Robinson said. “We see it in our community. I think everybody is doing everything they can to try to help it. The biggest thing is the vaccination because it does save lives.”

The NFL implemented strict protocols and daily testing to play a full but disrupted 2020 season. Stadiums were empty or at most partially filled. Rescheduled games were played on a few Tuesdays and on a Wednesday. The San Francisco 49ers were forced to relocate. The Denver Broncos lost a game for which all of the quarterbacks on their roster were ineligible. The Cleveland Browns won a playoff game with their coach in isolation in his basement.

Fingers are crossed that this season will be closer to normal.

“I’m very optimistic about the season ahead,” Sills said. “I think our league last year and our entire environment showed tremendous resilience and collaboration and the willingness to adapt. Though I think we’re off to a solid start, we know that there’s much more work to be done. And we will just have to continue to evolve as the data takes us there.”