Kevin Durant did not train on Tuesday and is questionable for Golden State's Western Conference playoff clash with Portland, team officials said.
Durant, who suffered a left calf strain while scoring 32 points in the Warriors' Game 1 win on Sunday, could be seen clutching his leg throughout the victory.
Warriors coach Steve Kerr confirmed to reporters the forward was a doubt for Wednesday's Game 2 with the Trail Blazers.
"If he didn't practice, there's concern," Kerr told local media. "He's questionable."
Kerr said he expects Durant to return quickly but stressed no risks would be taken with the superstar who missed 19 games during the regular season with a knee injury.
"You have to be careful," Kerr said, adding that a final decision on Durant's fitness for Wednesday would be taken after the morning shootaround.
The Warriors are also facing fitness concerns over Shaun Livingston (finger) and Matt Barnes, who is on the mend from an ankle injury but could feature.