With the league facing a surge of positive COVID-19 tests, the NBA and the National Basketball Players Association are in talks centered around increased testing leaguewide for vaccinated players and staff, league sources told ESPN.

As of Wednesday morning, a total of 60 players have entered health and safety protocols this season, including 43 in the past two weeks. Thirteen players entered protocols Tuesday, by far the highest number of any day this regular season. The previous single-day high was four, which occurred Dec. 1, Dec. 4, Saturday and Monday.

The Chicago Bulls, Charlotte Hornets and Brooklyn Nets have been hit with outbreaks, and two-time NBA MVP Giannis Antetokounmpo of the Milwaukee Bucks entered protocols Tuesday.

While conversations regarding testing between the NBA and NBPA are ongoing, it's expected that there will also be increased testing leaguewide around the Christmas and New Year's holidays, including for those who are vaccinated, league sources said.

Ramped-up testing was also instituted around the Thanksgiving holiday, with the NBA and NBPA agreeing for every player and Tier 1 staffer -- anyone working within 15 feet of players -- to be tested daily from Nov. 28 to 30, including those who are vaccinated.

It's also expected that there will be further booster requirements for staff beyond Tier 1 staffers, league sources said. Currently, the NBA has imposed a Friday deadline for players who are eligible to receive booster shots, with those who don't facing stricter protocols, including game-day testing.

Regarding staff, the NBA noted in a previous memo that eligible staff who have not yet received a booster would no longer be permitted to interact in person with players, travel with the team or otherwise continue as "Tier 1 Personnel," with limited exceptions.

Team executives and team health officials have in recent days described a sense of frustration regarding players who have tested positive but are asymptomatic, as these team officials said they're hopeful that the league can one day -- perhaps soon -- reach a point when only players who are feeling ill will be sidelined.

But the NBA remains mindful, league sources said, that those who are asymptomatic could still transmit the virus, and the league remains committed to following guidance from the CDC, WHO and its own infectious disease experts.

Even though 97% of players are vaccinated, some team executives and team health officials expressed concern before the season that the NBA wouldn't enter the season testing all vaccinated players in a break from policies used the previous season. Under such a circumstance, keeping track of the virus amid potential breakthrough cases, these team officials said, would prove challenging. But it was also understood around the league that daily testing in a largely vaccinated league likely wouldn't receive enough buy-in to be approved or enforced, these team officials said.

"I'm actually fine with it if we understand the risk factors," one Western Conference GM told ESPN regarding the lack of daily testing for all vaccinated players.

The league is hopeful that more players and staff receiving booster shots would improve immunity, but it would seem unlikely that the league, in accordance with the NBPA, would mandate boosters, league sources said. The NBA reached roughly a 97% vaccination rate without mandating vaccination, and there's optimism that it could reach similar numbers for booster shots without mandating them.

There's skepticism around the league that the recent uptick, which many team executives and team health officials say was predicted months ago, would cause any shutdown, though more postponements are expected. Multiple NBA general managers noted that the league powered through last winter's COVID-19 surge, even though there were several postponed games, and was able to finish the season and crown a champion.

But there's definite rising concern among team health officials and team executives who see other leagues facing their own outbreaks and game postponements or cancellations.

"We are pretty much defenseless now -- not against getting sick but against transmission and contraction," said one Western Conference head athletic trainer.

ESPN's Adrian Wojnarowski contributed to this report.