He needed assistance walking off the field after stumbling over first base on a groundout in the third inning of Miami's 5-0 loss.
Rojas could land on the IL, spoiling what has been a breakout season for the 30-year-old, who is hitting .289 with four home runs and 33 RBIs and plays stellar defense.
He's scheduled to get an MRI when the team returns to Miami on Wednesday.
"It wasn't pretty,'' manager Don Mattingly said. "And when we first got out there, I think he felt like his knee just kind of blew up.''
The Associated Press contributed to this report.