Conley suffered a facial injury when he was inadvertently elbowed on the side of his face by Blazers guard C.J. McCollum during the Grizzlies' 115-109 win on Saturday.
While the Grizzlies confirmed that Conley has returned to Memphis for further tests, they refused to disclose whether he had sustained a concussion or some kind of facial fracture.
"We've flown him back to Memphis to be re-evaluated, and we should know more about him [Monday]," Grizzlies coach Dave Joerger told reporters. "[It feels] awful. He's got the biggest heart. He's the purest heart guy and is a true leader who will do whatever is asked of him. It's a big blow, but we'll know a lot more [soon]."
Meanwhile, Grizzlies center Marc Gasol admitted that the team are going to miss Conley during Game 4 since he has averaged 16 points, 1.7 rebounds, 3.7 assists and 1.0 steals in the first three games of the series.
"I feel bad," Gasol said. "Of course I want Mike to be out there because I know how competitive he is and how much he wants to play.
"But sadly, this is a part of the game. Things happen, and it's a physical game. But he's OK. He was in good spirits."