"We'll let you know," Harbaugh said. "We'll see when the time comes."
This has been one of the strangest weeks in Ravens postseason history. Jackson missed his sixth full week of practice because of a sprained knee and then surprised the team by tweeting out Thursday night that his injury was more severe than originally believed. Huntley, his top backup, has been dealing with tendinitis in his throwing shoulder and didn't start throwing again until Thursday.
The only healthy quarterback on the team's 53-man roster is Brown, who has one career start.
The Ravens listed Huntley as questionable on the injury report, but he was a full participant Friday after being limited all week. Huntley estimated his right shoulder is "pushing around 90 to 99" percent.
Asked if he's been told that he would start Sunday night, Huntley said, "It's all game-time decisions."
The Ravens officially ruled out Jackson on Friday, although the quarterback essentially ruled himself out with his social media post Thursday. Jackson tweeted that his knee "remains unstable" and classified it as a "PCL Grade sprain, on the borderline of a strain 3."
Harbaugh said he did not know Jackson was sending that tweet.
"That's not something we can comment on," Harbaugh said. "The nature of an injury specific, the only person that comment on is the person. There are laws along those lines. We're educated by the league in terms of what we're allowed to say and what we're not allowed to say. That's nothing I can ever begin to comment on."
Jackson is finishing out the fifth-year option on his rookie contract and has no guaranteed money beyond this season. If an extension can't be reached by March, Baltimore would have to use the franchise tag on Jackson to keep him from becoming an unrestricted free agent.
Asked if Jackson was out for the entire postseason, Harbaugh said, "I don't know."
The Ravens initially described Jackson's injury prognosis as "week-to-week" and indicated it wasn't a season-ending injury. Jackson will now miss his sixth straight game on Sunday.
"That's why it's so challenging to stand here, and you get asked questions about injuries all the time," Harbaugh said. "You don't always know. Sometimes you're hopeful that it will be quicker. 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. That's why it's really tough to say."
In five games without Jackson this season, the Ravens have a 2-3 record and have failed to score more than 17 points. In four starts, Huntley has passed for 471 yards, throwing for two touchdowns with two interceptions. Brown made his first career start Sunday, when he threw two interceptions and fumbled once in a loss to the Bengals.