As Warriors coach Steve Kerr was driving to work last week ahead of Game 4 of the Western Conference semifinals series, his focus wasn’t on the Memphis Grizzlies, but rather on his cough, his congestion and the cases of COVID-19 that had popped up at the team’s San Francisco facility.

The NBA made testing for the disease — once mandatory and daily — an effectively voluntary practice for vaccinated players and coaches this season. In February, Kerr had, like so many of us, stopped wearing a mask when he was at work, on the sidelines. No one actually likes wearing them.

But Kerr was concerned enough that he put the mask back on for Game 3 of the series on the first weekend in May.

Then, Kerr tested positive for COVID-19 two hours before Game 4. He missed that game, as well as Games 5 and 6 — as the Warriors clinched the series — and has now recovered from the “mild” case and will be on the sidelines fortonight’s start to the Western Conference finals against the Dallas Mavericks.“I just felt like ‘I better test,’ ” Kerr said, recalling his mindset on the drive to Chase Center. “If I pass this on to the team, I’ll never forgive myself.”

With new COVID-19 cases rising threefold since the start of April, this disease offers a new threat to not only the Warriors, but the NBA as a whole.

It could absolutely determine the league’s champion in June.

Clippers star Paul George missed his team’s win-or-go-home play-in tournament game last month with COVID-19. George was symptomatic and tested positive. His team went home.

In the Warriors’ last series against the Grizzlies, Memphis big man Steven Adams missed the first two games after testing positive for COVID-19. Given how well he played once he did enter the fray, one can only wonder how affected Memphis was by his absence.

Then on Tuesday, the Celtics announced that center Al Horford would miss Game 1 of the Eastern Conference Finals against the Heat, as he has entered the league’s health and safety protocols. It’s a blow that will unquestionably change the complexion of that series.

If Steph Curry or Draymond Green were to test positive in the coming days, the Warriors’ title hopes would unquestionably turn negative.

That’s why Kerr’s positive test, while it did not create a significant issue for the Warriors, does serve as a warning.

“This is still something we have to be alert with and protect against and have precaution in terms of how you’re moving through your day and who you’re going and who you’re around — how you spend your time outside this facility,” Curry said. “It’s a very sensitive time … you pray that it does not influence the way that this season ends.”

COVID-19 cases are increasing across the Bay Area: As of Monday, new reported cases are up more than 40% over the last two weeks in San Francisco where the team plays and many players and staff live, 58% in Alameda County, 85% in Marin County and 41% in San Mateo County.

“It was just kind of my turn,” Kerr said of his stint off the Warriors bench. “It seems like, last couple of years, practically everybody on our coaching staff and our team has had it at some point.”

We’ve come a long way since the beginning of the pandemic in this country — a moment that cannot be officially pinpointed but is often associated with the NBA and Utah Jazz center Rudy Gobert’s positive test in Oklahoma City, which shut down the league for months.

I’m told that the league has no hard and fast rule on postponing playoff games, outside of the eight-player limit. Given that there are only four teams remaining, the league can also take a more case-by-case approach, should a COVID-19 situation arise, looking at things like cycle threshold values, which can measure how contagious a positive test is.

And while games can be moved — World Series games are rained out all the time — with millions in ad revenue on the line, the NBA is obviously not keen to ask its television partners to shuffle their schedules at this juncture of the season.

“We continue to consult with doctors, infectious disease specialists and epidemiologists on COVID-19 cases that arise and are prepared to do what is necessary to keep our teams and players safe and healthy,” an NBA spokesperson told this news organization. “That said, we are comfortable with the current health and safety protocols that we have in place with the Players Association and are hopeful we’ll be able to complete the postseason and crown a champion, as we did each of the last two years, without any schedule changes.”

In short: We’re on it, and the games will go on.

Luckily, postponing games has not proved necessary since the calendar flipped to 2022, and the league is confident that will not change now.

But the disease can still have a huge effect on these critical games.

And while the Warriors are fully vaccinated — once a requirement to play games in San Francisco — the current, circulating subvariants of omicron have shown an ability to elude vaccines and re-infect those with natural immunity.

On the court, every athletic action could bring about a negative consequence. Every drive to the basket carries the risk of a hard foul or a twisted ankle. The injury threat is omnipresent, especially in physical playoff games, but it’s mostly compartmentalized to game action.

With COVID-19 on the rise again, there’s an omnipresent, invisible threat to winning a title off the court, as well.

“So far, so good,” Curry said. “We’ll just try to control what we can control.”