The 23-year-old linebacker, taken in the second round of the draft out of the University of Texas, was listed in stable condition in a Texas hospital after apparently tumbling down some stairs at a house he was visiting Thursday.
"Members of our medical staff...have spoken with doctors in Texas," Ravens general manager and executive vice president Ozzie Newsome said in a statement. "We understand Sergio is stable at this time and that he is being tested and observed."
The Baltimore Sun cited a league source as saying Kindle's condition had improved over the last few days and he was expected to make a full recovery.
The 6-foot-3 (1.91m), 250-pound (113kg) Kindle has not yet signed with the National Football League club.
(Writing by Larry Fine in New York, Editing by Steve Ginsburg)