When Dr. Jonathan Drezner considered how much is still unknown about COVID-19, he just couldn’t recommend that Pac-12 colleges play football or any other sport this fall.

Drezner is the director of the University of Washington Medical Center for Sports Cardiology, a team physician for the Washington Huskies, and one of the medical experts advising Pac-12 universities on their decision. The state of the pandemic is worse than expected, Drezner said, and there is still too much unknown about the effects of COVID-19, including increasing concerns on the impact it has on the heart.

“Across the Pac-12, there are a number of cities where the pandemic is uncontrolled,’’ he said Wednesday. “Where testing is not available, quick turnaround time for testing is not attainable. There’s so much unknown, and we don’t have the testing infrastructure to protect our athletes.’’

Yet in his side gig, Drezner is a team physician for the Seattle Seahawks, helping the NFL figure out how to play its season. The NFL and NFL Players Association tabbed Drezner to lead a COVID-19 subcommittee on treatment and management this summer. And even though he doesn’t believe Pac-12 schools should be playing sports this fall, he doesn’t have an issue with the NFL moving ahead.

“It’s a very big difference,’’ Drezner said. “There’s a whole infrastructure that’s needed, and the NFL did a fantastic job in setting up what they have done for testing. To me, that’s different, and I don’t believe it can be replicated in a college setting.’’

The NFL’s war on COVID-19 has seemingly worked well over the first three weeks, better perhaps than some inside the league expected.

The NFL, armed with billionaire owners and billions of dollars in league revenue, hired BioReference Laboratories to set up 32 testing sites and produce the capacity to test thousands of players and employees every day. Players who test positive are immediately quarantined before entering the team facility and cannot return until they pass a series of tests.

Every player, coach, staffer, locker room attendant, and cafeteria worker is tested daily, and according to the NFL, the league processed 109,075 tests over its first 21 days (about 5,200 per day).

By comparison, the NHL conducted about 14,000 tests in a similar time frame.

When crafting the testing policies this summer, the NFL and NFLPA hoped to keep the positivity rate below 5 percent. If that came to pass, the NFL would switch from daily testing to every other day after two weeks.

But the actual rates have been far lower. During the initial “intake’’ period, when players and all staffers had to pass three tests in four days just to get access to the facility, only 1.7 percent of all people tested positive (players were at 1.9 percent). And since that intake period, the positivity rate is 0.46 percent (0.81 percent for players). No team has had a rate over 1.7 percent.

“We were pleasantly surprised at how few positive tests we had,’’ said Dr. Allen Sills, the NFL’s chief medical officer. “Given the fact that our clubs were coming together and we had players who were coming from a large number of hot-spot areas, I would not have been surprised if the numbers had been substantially higher.’’

Even with the encouraging results, the NFL and NFLPA agreed on Wednesday to continue daily testing through Sept. 5. The concern is that teams are now moving more toward group-based activities with the start of actual practices. The NFL has also purchased point-of-care rapid testing machines that should enable players to get even quicker results.

“We and the PA together felt it was prudent to extend the daily testing through Sept. 5,’’ Sills said.

Of course, the testing itself doesn’t prevent the players from getting COVID-19 or create the low positivity rates. But the NFL at least has a well-coordinated and well-funded system of testing, tracing, and quarantining to keep the virus out as best it can.

And the NFL universe is tiny compared with college sports. The NFL ecosystem encompasses about 5,200 people. But college sports has hundreds of schools, and thousands upon thousands of athletes playing football, volleyball, field hockey, and other sports.

“It’s not just football. Some schools have 600 to 1,000 athletes, and the costs would be enormous,’’ Drezner said. “And not only that, but it takes personnel to print out the labels and do the swabs and the chain of custody for the specimens and all that kind of stuff that’s so critical and, really, taking time from athletic trainers across the nation.’’

There is also the ethical debate at play in trying to play sports during a pandemic. The virus is still raging in parts of the country, and there are still many unknowns when it comes to COVID-19 side effects. Experts have recently become alarmed at increasing anecdotal evidence of heart problems (myocarditis) developed by COVID-19 patients, regardless of whether the person was asymptomatic or had severe symptoms.

It’s one thing for the NFL to forge ahead, where the players are consenting adults who can make their own decisions, and have daily testing and massive resources at their disposal. It’s another to ask college students to be the guinea pigs.

And without daily testing, is it right to bring large groups of student-athletes together to potentially spread the virus?

“Yes, most individuals have a mild case and do very well, but there are occasionally people who get very sick or have long-term problems,’’ Drezner said. “The bottom line is we want to protect our athletes from getting infected because of sports, because we’re worried about a variety of different health outcomes.

“If our pandemic was in a different place, if we had a low prevalence in all these communities, if we had adequate testing, even with our concerns with the heart or lungs or things, we really might be able to move forward with sports as we once knew it. And I’m hopeful at some point that that’s where we’re going to be. But to get there we might need more time.’’

TESTING 1-2-3

More COVID-19 news and notes

Yes, I know many readers are tired of COVID-19 and want to get back to football. I promise, we will get there. But training camp practices don’t really start until Monday. And I believe it is important to chronicle the NFL’s COVID-19 experiment closely and accurately.

A few more testing-related notes:

■ The NFL’s positivity rate is actually lower than what it reported. The official numbers are 1.7 percent during the initial four-day period, and 0.46 percent since. But the NFL is including all positive tests, when in reality a positive test doesn’t necessarily equal a new infection.

Dr. Allen Sills, the league’s chief medical officer, said the NFL is splitting the positives into three categories — “unconfirmed’’ positives, when a player has one positive test surrounded by several negatives; “persistent’’ positives, where a player who had the virus weeks or months ago is recovered but still turns up positive because he has remaining viral debris in his system; and “new infections.’’

The third category is the one with which the NFL is really concerned.

“How many new COVID infections are we detecting? That’s really the measure of infection control that we’re interested in,’’ Sills said. “Just reporting a number of positive tests doesn’t really give you that data piece.’’

■ As of Thursday, 16 of 108 players that have been placed on COVID-19 injured reserve had a stay of 15 days or longer (15 of the players are still on the list, with the longest stay at 18 days as of Friday). But Sills said that none of the players have come down with a “severe’’ case of COVID-19.

■ Just because 108 players went on COVID-19 IR doesn’t mean that 108 players tested positive. In fact, the NFLPA said that as of Wednesday, only 64 players had tested positive since training camps began. The other 40-plus players to go on COVID-19 IR are likely a close contact of someone who had the virus, or perhaps a false positive. Of the 108 players on the list, 24 came off in three days or fewer.

■ Dolphins rookie defensive tackle Benito Jones is the only player to go on COVID-19 IR twice — for two days each on July 27 and Aug. 6. Given his short stays, it doesn’t appear that he tested positive either time.

■ Chargers coach Anthony Lynn revealed on “Hard Knocks’’ that he caught the virus at some point before camp, and ESPN reported Friday that nine coaches have tested positive since camps began. Eagles coach Doug Pederson is back in the offices after testing positive on Aug. 2.

■ Will the NFL cancel or postpone a game if there is an outbreak on a team on a Saturday or Sunday? It is still being negotiated between the NFL and the NFLPA, and it likely will include flexibility instead of concrete numbers.

“We’re still finalizing some aspects of the game-day protocols,’’ Sills said. “We will have a very specific protocol in place as to what testing and reporting looks like, but it’s hard to make exact number cutoffs.’’

■ Friday, five game officials (none referees) opted out of the season. The NFL negotiated an opt-out deal with the NFL Referees Association, allowing officials to receive a $30,000 payment this year and have job security for 2021.

The NFL now has 114 officials on the roster for 2020, which is enough. But the league may still add a few more temporary replacements.

ETC.

2021 Combine hugely important

Set a reminder on your calendars to watch the NFL Combine next February and March. It’s going to be must-watch TV.

The Pac-12 and Big Ten already have canceled their football seasons, as have the MAC and other small conferences. Several other leagues are still considering their seasons.

The Combine will be the next time that scouts and fans will get to watch the Big Ten and Pac-12 draft prospects perform football drills.

“This year’s NFL Scouting Combine will be the most important one in league history,’’ said NFL Network’s Dan Jeremiah, a former scout. “We always preach, ‘It’s all about the tape,’ but if you haven’t seen a player on grass in over a year, this event will take on a whole new meaning.’’

It’s still possible that college football will be played in the spring, but it would be a lot to ask players to put their bodies through even an abbreviated spring season, then play again in the fall.

But should there be some sort of spring football, the NFL can adjust its calendar. The collective bargaining agreement states that commissioner Roger Goodell can hold the draft as late as June 2 without having to consult the NFLPA.

More likely, not having a 2020 college football season will undoubtedly make it difficult to scout next year’s prospects, and will certainly cost players a chance to improve their draft stock. Joe Burrow was probably a late-round draft pick entering the 2019 season, and he finished as the unquestioned No. 1 pick.

“If this happened a year ago I may be looking for a job right now,’’ Burrow tweeted.

Going according to plan

The NFL has proceeded full speed ahead since the pandemic began, holding free agency, the draft, and the start of training camps on time. So it shouldn’t come as much surprise that the league is taking the same approach with February’s Super Bowl LV in Tampa.

“We’re very confident in our protocols and are very focused on a Super Bowl and a season that ends on Feb. 7 and starts and ends as scheduled,’’ NFL executive vice president Peter O’Reilly said Tuesday.

The biggest change is that the league’s “NFL Experience’’ — a museum-type of atmosphere where fans can run a 40-yard dash and view football memorabilia — will be held outside along a 2.7-mile stretch of the Tampa Riverwalk. Typically, the Experience is indoors in a convention center.

Otherwise, the only focus is getting the game in.

“If there needs to be adjustments, we’ll be ready to make them,’’ said Rob Higgins, chairman of the host committee. “At this point in time, there haven’t been any adjustments. We just continue to plan.’’

A running total

In researching a story this past week about Cam Newton and his scrambling ability, I was struck by how dominant and productive he and Russell Wilson have been compared with other mobile quarterbacks throughout NFL history.

Newton is third all time in rushing yards (4,806), while Wilson is fifth (3,993). Yet Newton has played only nine years, and Wilson only eight.

Newton and Wilson already have more rushing yards than Fran Tarkenton (3,674), who played 18 seasons. They have more rushing yards than the great John Elway (3,407), who played 16 years. Soon enough they will both pass Randall Cunningham, (4,928 yards), who also played 16.

Michael Vick is the all-time leader at 6,109 yards in 13 seasons. His record doesn’t feel safe.

Extra points

The Chiefs are keeping the band together, signing Patrick Mahomes, Travis Kelce, and Chris Jones to contract extensions this offseason despite having little cap money. Most impressively is that the Chiefs signed Mahomes and Kelce to team-friendly deals — Mahomes only got $10 million up front and gave the Chiefs control over his contract for the next 12 years, while Kelce signed an extension on Thursday that pays him zero extra money in 2020. The allure of “let’s keep this together’’ was likely strong in convincing the players to take team-friendly deals . . . When Patriots quarterback Brian Hoyer mentioned two Fridays ago that his family now lives in New England full time, my first thought was, “How long until he joins the Patriots’ coaching staff?’’ Hoyer, who turns 35 in October, seems like a natural fit as a quarterbacks coach and potential offensive coordinator in the not too distant future . . . Sean McDermott received a well-deserved contract extension from the Bills this past week. He has brought the Bills back to respectability, ending a 17-year playoff drought and leading them to the postseason in two of the last three years. Now the real task at hand — find a quarterback. It may be Josh Allen, but the Bills aren’t going any further until they get better play at the position.

Ben Volin can be reached at ben.volin@globe.com. Follow him on Twitter @BenVolin