"We know he's getting better every single day," Harbaugh said after the Ravens' practice at Navy. "Obviously, we have a plan for him, football-wise, when he gets back. But we haven't been told when yet."
Doctors told Flacco and the Ravens that he would need about a week of rest in order to recover from a back injury.
Harbaugh said last week that he is confident that Flacco will be back long before the end of the preseason. On Wednesday, Harbaugh said all indications from Flacco and trainer Mark Smith have been "very positive."
With Flacco out, Ryan Mallett has been working with the first-team offense. The Ravens signed inexperienced quarterbacks David Olson and Josh Woodrum because it has always been believed that Flacco would be out for only a short period.
In his only comments about the injury, Flacco said on July 28 that he was unsure when he would return to practice.
"Hopefully not too long, but at the same time, it is kind of a waiting game," Flacco said. "It is just one of those things where you have to be patient and not let your competitive nature get the best of you. I am talking about everybody -- myself and, really, everybody."