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In a blow to keeping players in game shape during the coronavirus pandemic, the NBA issued a memo to the players’ union stating team practice facilities are to be closed starting Friday. It also prohibits players from working out in public gyms or at universities.

The edict doesn’t bode well for picking up the regular season with all 30 clubs. According to an NBA source, one of the several contingency plans is reviving the season with just 16 teams — the current top eight seeds in each conference — to start the playoffs.

Thursday’s notification departs from a memo sent two days earlier in which individual players were allowed to report to their teams’ facilities to work privately, but kept away from teammates.

The Knicks also have been advised to be in self-quarantine because they faced Rudy Gobert, Donovan Mitchell and Christian Wood earlier this month and all three since have tested positive for the coronavirus.

According to the memo obtained by The Post: “Effective tomorrow, March 20, and until further notice, team practice and training facilities (including the facilities of teams’ G League affiliates) will be closed to players and staff. This directive is consistent with an increasing number of state and local government restrictions, and an emerging consensus regarding how to mitigate the spread of the coronavirus with which the NBA’s infectious disease and public health experts agree.

“Players are thus prohibited from using public health clubs, fitness centers, gyms, college facilities, or the like,’’ it read. “With the team facilities closed, teams are now prohibited from organizing or engaging with players in any group or individual practices or workouts. Teams may provide players with training, conditioning or other instructional materials for players to use at their homes, if they so choose.”

The Post reported earlier this week players could travel out of their home markets as long as they stay in North America. The new message still permits it, but appears to discourage such travel.

In addition, the letter to the union asks players not to work out at gyms other than in their own homes, encouraging self-isolation.

“As a general matter, players are recommended to remain in their team markets and avoid all non-essential travel,’’ the letter read. “If a player, following coordination and consultation with his team, travels away from the team’s market, he should travel to his destination and stay in that city. Players should continue to take aggressive measures to avoid contact with others and remain home as much as possible, leaving only for essential activities, such as buying food, medicine, or other necessary supplies; obtaining critical medical services; providing necessary care for a family member in another household; or attending to some other emergency.”

The Post has reported Mitchell Robinson and Elfrid Payton flew to New Orleans. A social media photo appears to show Damyean Dotson in Houston with a trainer after a gym workout.

The Knicks released a statement Wednesday night confirming The Post’s report of last Thursday that, in keeping with Centers for Disease Control and Prevention guidelines, their players won’t be tested for coronavirus without symptoms. The statement said no Knicks had shown symptoms.