The presumption has been that Tyler Huntley, who missed last week's game due to a shoulder injury, will get the start, but the quarterback was equally mum on the situation.
"It's a game-time decision," he said Friday when asked if he's been told he would start.
Huntley said the rest last week helped his injured shoulder.
"Shoot, it's up there, it's a good percentage. I think we're pushing 90, 99, around there," he said. "We're up there. We practiced today, and we're just seeing how we're gonna feel these next couple days."
Added the 24-year-old QB: "With seeing the same team two weeks in a row, that was a good thing that I did rest. I'm feeling even better as we speak right now."
Huntley is officially questionable to play against Cincinnati after practicing fully Friday. If Huntley can't go, rookie quarterback Anthony Brown would make his second straight start.
The Ravens offense has struggled without Jackson, averaging 12.5 points per game the past five contests, second-fewest in the NFL behind the Jets (11.0 PPG) in Weeks 13-18, 17 points fewer than Weeks 1-12.
If healthy enough to play, Huntley would make his first career postseason start.
"No nerves," he said. "Just excited to get back out there, missing one week. It's just another opportunity to go play football and I appreciate it, and to be doing it with the Ravens, that puts it over the top."
As for Jackson, who tweeted an update on his PCL injury Thursday, noting he hasn't been able to get healthy enough to return, Harbaugh said Friday he "didn't pay attention" to the tweet and couldn't comment on the former MVP's condition.
Harbaugh added the Ravens "can't know" if Jackson might be available for the postseason should Baltimore win Sunday night.
"Here's the thing: You don't know," the coach said. "That's why it's so challenging to stand here, and you get asked questions about injuries all the time and you understand it 'cause it's important, and you don't always know. Sometimes you're hopeful it'll be quicker. I know I'm always hopeful that guys get back quicker, that it's the front end of any kind of a prediction. Sometimes it goes the other way, and it's longer, and you're disappointed. "