Derrick Rose was forced to leave the Chicago Bulls' game against the Portland Trail Blazers with a knee injury.
The 2011 MVP, who missed all of last season while recovering from an anterior cruciate ligament tear, will undergo an MRI scan to determine the extent of the injury later today.
Head coach Tom Thibodeau told reporters: "He has pain and he felt like he couldn't push off his right knee.
"I'm concerned. Any time anyone goes down, you're concerned, but I don't want to speculate until we get more information for you guys. We'll have more [Saturday] for you guys.
"I know how much work he's put into his rehab, the type of person he is, the type of player he is. So concern for that, I feel for him because of all the things he does mean to our team."
After the 98-95 defeat, Rose left the trainer's room on crutches.
