Sources say that Rondo, who suffered the injury in the first quarter of Saturday night's win in Orlando, was scheduled to be evaluated extensively Sunday by the Mavericks' medical staff to establish a firm timetable on how long he'll be sidelined.
But Rondo has already been ruled out of the Mavericks' home game Monday night against the Timberwolves, who will be welcoming Ricky Rubio back to the lineup after his 42-game absence thanks to an ankle injury.
"It was a really bad collision," Mavericks center Tyson Chandler said of the shot Rondo took to the head just 98 seconds into Saturday's game. "I don't know what the prognosis is, but he is pretty beat up."
On the play in question, Rondo tripped over the leg of Magic guard Elfrid Payton and then was accidentally kneed in the face by teammate Richard Jefferson, who did not see Rondo on the floor as he started to sprint down the court on a fast break.
With blood pouring out of his nose, Rondo stayed down on the court for about a minute before being escorted to the locker room by the Mavs' athletic training staff.
ESPN.com's Tim MacMahon and The Associated Press contributed to this report.