An MRI on McGrady's left knee Monday showed swelling in the tendon but no damage, according to the Houston Chronicle.
"There was no structural damage," Rockets trainer Keith Jones told the newspaper. "There was some inflammation in the tendon by the kneecap where the tendon starts. That's really it. Now, we stay aggressive with it. We'll change a few things and get it stronger and see where it goes. He's still day-to-day, and we'll see what happens."
McGrady, who is the Rockets' leading scorer at 22.8 points a game, left at halftime of Houston's loss at Detroit on Sunday after aggravating his knee.
McGrady injured the knee in the Rockets' loss to the Magic on Dec. 19. He then missed a loss at Denver the following day but returned to play 30 minutes in Saturday's defeat of Chicago, scoring 20 points along the way.
Houston plays at Memphis on Friday.
Information from The Associated Press contributed to this story.