The Brooklyn Nets are without part of their "Big Three" to kick off the 2021-22 season ... 'cause Kyrie Irving will not attend the team’s media day due to New York City's COVID-19 protocols.

Irving is believed to be in the roughly 10% of the league that has not been vaccinated ... with Rolling Stone reporting he's actively engaging with wild anti-vax conspiracies on social media.

Considering there's a mandate requiring NYC-based NBA players to have at least one vaccine shot before practicing or playing indoors, Irving had no choice but to miss the team's event on Monday ... and now, his status for the season is in jeopardy.

29-year-old Irving is coming off one of his best seasons as a pro ... dropping 26.9 points on 50.6% shooting and averaging 6.0 assists and 4.8 boards.

Irving certainly figures to be a crucial part of any hopes the BK Nets have to win a title this season ... but unless he gets a religious exception from the league (Andrew Wiggins' request was denied), there is a slim chance he can suit up until the city's protocols change.

Irving's teammate -- Kevin Durant -- was asked about why he isn't concerned about KI's vaccination status ... and he downplayed the whole situation.

"That's his personal decision," KD told the media. "What he does is not on us to speculate. I expect us to have our whole team at some point."

Now we all know, Irving marches to the beat of his own drum ... but that drum may not be at a championship parade if things don't change.

While his NYC availability is up in the air, Irving is expected to travel with the team to San Diego later Monday for training camp.

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