Golden State Warriors' leading scorer Kevin Durant will undergo an MRI scan after injuring his knee in his side's 112-108 loss at Washington Wizards.
Durant limped out of Tuesday's game in the first minute after team-mate Zaza Pachulia fell on his left leg.
"I'm always concerned because you never know how bad it's going to be," said Warriors coach Steve Kerr.
The 2014 NBA Most Valuable Player joined the Warriors this season in a deal worth a reported $54.3m (£43.9m).
Durant had spent the previous eight seasons at Oklahoma City Thunder, where he was a four-time NBA scoring champion.
Western Conference leaders Warriors went into the game with a league-best 50-9 record and have already booked their place in the play-offs.