Always and forever, baseball is consumed by numbers. A .300 batting average signals a good season; a 5.00 ERA not so much. Players are measured by WAR. Hall of Fame cases get built around proximity to 500 home runs, 300 wins, and other magical markers.

These days, though, only one metric matters: How many players test positive for COVID-19?

Not a single other statistic is relevant. Because as nearly 1,800 players reported to training camps in 30 cities across Major League Baseball this week and underwent requisite “intake screening” — a three-tiered process that involves a temperature check, a saliva or oral/nasal swab, and a blood sample for serology and antibody testing — the rate of COVID-19 infections could paint a clearer picture of whether this season-within-a-pandemic can reasonably move forward.

“There are going to be a steady number of players who test positive,” said Paul Sax, clinical director of infectious diseases at Brigham and Women’s Hospital in Boston. “That, I think, is something we’re going to have to expect.”

But what percentage of positive tests is manageable? What percentage would imperil the league’s plan to launch a 60-game season?

After consultation with the Players Association, MLB intends to release a broad overview of testing data — total tests administered and positives returned — on a semiregular basis and perhaps as soon as Friday. But the identities of the people who test positive won’t be revealed in accordance with medical privacy laws and terms of baseball’s collective bargaining agreement.

For that reason, Phillies manager Joe Girardi was unable to offer details on the condition of four players — infielder Scott Kingery, relievers Hector Neris and Tommy Hunter, and lefty Ranger Suarez — who went on the COVID-19 injured list in advance of Friday’s first official team workouts. Players can be placed on the list if they test positive, show symptoms, or have contact with an infected person.

(It’s unclear whether teams will even be required to differentiate between players on the COVID list and the regular injured list, although the absence of information about an injury would seemingly be a giveaway.)

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According to the COVID Tracking Project, 2,674,813 of the 32,827,359 reported tests in the United States have come back positive through Thursday evening. Based on that nationwide rate, could MLB expect roughly 8.1% of players to test positive?

“I don’t think we can apply a national number,” Sax said. “If you go to Arizona right now, it’s 20 to 25%; if you go to Boston, it’s 1½ to 2%. One thing that this virus is teaching us is that the likelihood of getting infected is very much dependent on where you are and what’s going on in your community.”

It might be an ominous sign, then, that cases are skyrocketing in Florida, Texas, Arizona, and California, states that are home to a large segment of major-league players and staff. Arizona has reported 332,769 cases — 59% of its overall total — since June 1, based on data at the COVID Tracking Project. Florida has reported 991,793 cases — 48.8% of its total — within that span.

Two weeks ago, the Phillies experienced an outbreak at their spring-training site in Florida. They tested 48 people and had 11 positives, a rate of 22.9%.

And whereas the elderly community was once considered far more susceptible to the virus, Sax noted that younger adults are being infected at a higher rate, too.

Three weeks ago, Sax expressed confidence that baseball could “make it as safe for [the players] as possible” and pull off a season. He’s less certain now.

“I can understand their wanting to play, but I would’ve also understood if they decided not to have a season this year at all,” said Sax, an avid baseball fan. “I think the same way that the virus spreads outside of baseball it will spread inside of baseball.

“If they’ve got crowding indoors and if people are not wearing masks, and if there’s someone there with the infection, it’s going to spread. If they’ve got [every-other-day] testing and they’re practicing social distancing and they’re not going to bars and restaurants, then we can keep it under control.”

Girardi said he’s had “numerous conversations” with players about the importance of responsible off-field behavior. Risk-taking, in all its forms, could derail the Phillies’ season.

But unlike other pro sports leagues, namely the NBA, MLB will attempt to conduct a season without quarantining teams in one location or a few hub cities. Playing baseball in home cities, even with only regional travel and strict behavioral protocols (no leaving the hotel on the road except to go to the ballpark, for instance) presents considerable challenges.

“If you make a mistake, you jeopardize yourself, you jeopardize your family, you jeopardize your teammates and their families and our chances of winning. That was spelled out,” Girardi said on a Zoom conference call.

“And it’s been spelled out at different times because there’s a huge responsibility. People are not used to being isolated. They’re not used to not seeing friends when they want to or going to get something to eat when they want. But for us to make this work, we’re going to have to do that.”

If the enormity of the undertaking wasn’t already clear, Sax suggested the results of the intake screening could reinforce the point.

“I don’t want to jinx it, but it would not surprise me if, in at least one team, there’s a cluster of cases and then something’s going to have to happen,” Sax said. “I wonder if they’re going to be able to complete the season.”

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