Harbaugh declined to name a starter during a Friday news conference, even indicating that Joe Flacco could still play.
That Harbaugh would keep a decision close to the vest doesn't come as a surprise in a world where NFL teams prefer to not give an opponent an advantage for preparation purposes.
Flacco, though, is listed as doubtful on the injury report, which is not a surprise as he hasn't practiced the entire week while he deals with a hip injury.
The obvious choices are either rookie Lamar Jackson or veteran Robert Griffin III. Jackson returned to practice Friday after missing the previous day with an illness, while Griffin got in a lot of work with the first-team unit Thursday. It is unknown whether Griffin or Jackson took the majority of practice repetitions Friday.
Still, one thing is clear regardless of starting quarterback ahead of Sunday's game. The Ravens are entering must-win territory with a 4-5 record and sit two games out of first place in the AFC North.