The Indiana Pacers' George snapped his lower right leg on Friday, prompting a United States intra-squad game in Las Vegas to be called off.
In the fourth quarter of the exhibition game - part of the USA's preparations for the 2014 FIBA World Cup in Spain - George broke his leg when attempting to stop James Harden scoring on a lay-up.
It led to a flurry of support from George's fellow NBA stars on Twitter, with both #PrayForPaulGeorge and #PG24 trending worldwide.
LeBron James, a four-time MVP, tweeted: "Man just landed and got a message about @Paul_George24. Made me immediately sick to my stomach!! Praying for u a speedy recovery homie!!!"
"God bless u my brother @Paul_George24. Im hurt, praying for you. Praying for peace. Praying that God heals you in a supernatural way," wrote Kevin Durant, who was playing in the intra-squad game.
Miami Heat star Dwyane Wade wished George the best, praising the 24-year-old's character.
"Praying for @Paul_George24 for not only the player he is but the person he is. Injuries are thee toughest part of sports," he tweeted.
Golden State Warriors point guard Stephen Curry hoped George, a two-time All-Star, would return a better player.
He tweeted: "Pray for PG and his family! Pray for the Doctors overseeing his recovery and that he comes back stronger than before. #USA"
Later, George thanked everyone for their support and promised to return 'better than ever'.
In a statement, the Pacers said they were greatly concerned and that their thoughts and prayers were with George.
The team expect to have more details on Saturday.