OAKLAND, Calif. – The initial hit caused Klay Thompson plenty of pain. The final diagnosis delivered another blow to him and the Golden State Warriors as they prepare for the NBA Finals. Two days after he got kneed in the head by Houston’s Trevor Ariza, the Warriors said Friday that Thompson has a concussion and will not return to practice until he is symptom-free. The All-Star guard went through neurological tests that confirmed the concussion. He was injured in the fourth quarter of Golden State’s 104-90 win over the Rockets in the Western Conference finals clincher on Wednesday. The NBA Finals start Thursday against Cleveland. And while the Warriors are optimistic Thompson will be cleared before then, he must first pass through the league’s concussion protocol. “This break has turned out to be good for us,” Warriors coach Steve Kerr said after Friday’s practice. “And maybe good for Cleveland, too, because they’ve got some injuries.” Cavaliers guard Kyrie Irving has been slowed by knee tendinitis and a sore foot, and four-time NBA MVP LeBron James has been banged up as well. But neither of those injuries seems as serious as the one the Warriors are facing now. It’s unclear how long Thompson could be away from the court. The NBA’s concussion policy requires players to pass a series of steps without experiencing symptoms before they can return. That starts with riding a stationary bike and progresses to jogging, agility work and non-contact team drills. The protocol also requires the team physician to discuss the process with the director of the NBA’s concussion program.