Klay Thompson faces a race against time to be fit for the Golden State Warriors' NBA Finals opener against the Cleveland Cavaliers after suffering a concussion.
The guard took a knee to the head from Houston Rockets forward Trevor Ariza during Game 5 of the Warriors' 4-1 Western Conference Finals series victory on Wednesday.
Thompson's father earlier stated that he was "on track" to play in the finals, but the Warriors have cast doubt on his involvement.
A statement from the Warriors read: "Following extensive examinations over the last two days - including neurological tests earlier this morning - Warriors' guard Klay Thompson has been diagnosed with concussion.
"He will not return to the court until he is symptom-free and cleared under the NBA's concussion protocol guidelines. He will be evaluated daily and there is no timetable for his return."
Thompson originally returned to action during Wednesday's win that ensured the Warriors a return to the NBA Finals for the first time in 40 years.
However, his father later said that he had to be driven home and vomited a couple of times.
Thompson has until Thursday to be cleared by the NBA, when Cleveland travels to California to play Golden State in Game 1 of the NBA Finals.