Flacco has not practiced at all because of a back injury that he reported to the team on the eve of the first training camp workout. The Ravens initially hoped he'd miss just a week, but they announced two weeks later that while Flacco wouldn't play in any preseason games, he would return to practice during the preseason.
Harbaugh said the team is just waiting medical clearance before Flacco gets back on the field.
"We don't know that date [and] when that's going to happen right now," Harbaugh said. "We believe it's going to be real soon in time to prepare for Cincinnati and then he'll be out there."
Before he started throwing in the past couple of days, Flacco has been focused on the rehabilitation process.
"He's been working on that. He's worked very hard on that," Harbaugh said. "I do believe he's in good shape; I wouldn't say football shape because he hasn't played football, but he's in really good shape as far as conditioning, his cardiovascular, his strength and those kinds of things. Those are things that we'll have to wait and see when he comes out to practice."
Harbaugh also said wide receiver Breshad Perriman, who has been sidelined since Aug. 1 after he sustained a significant hamstring injury, is getting closer to practicing.
"I'm optimistic that he'll be practicing very soon [and] he'll play against Cincinnati," Harbaugh said. "I'm very optimistic on that. That's barring any kind of setback."