Milwaukee Bucks' Giannis Antetokounmpo was forced off with a knee injury as they suffered a 110-88 defeat by the Atlanta Hawks that levels their Eastern Conference finals series at 2-2.
Antetokounmpo, 26, had to be helped off court and back to the locker room after landing awkwardly in the third quarter.
He returned unaided to watch from the sidelines, but faces further tests to determine the severity of the injury.
"You lose your best player, it stinks," said Bucks forward PJ Tucker.
"But this is the Eastern Conference Finals. There is no excuse. It doesn't matter whoever is playing, not playing.
"They've got guys hurt. Everybody is hurt. Everybody is banged up. Everybody is injured. You've got to fight through it."
The Bucks trailed by 10 points at the time of Antetokounmpo's injury, but were 25 points behind by the end of the quarter as the Hawks took full advantage of the two-time NBA Most Valuable Player's absence.
Lou Williams, in for the injured Trae Young, top-scored for Atlanta with 21 points while Bogdan Bogdanovic added 20 points, with six Atlanta players finishing in double figures.
"It was a total team effort and guys continue to step in and take advantage of opportunities when they get them," said Hawks coach Nate McMillan.
Game five of the best-of-seven series is in Milwaukee on Thursday.