Flacco has missed close to a month of practice because of a back injury. However, he will be ready for the regular-season opener Sept. 10 against the Cincinnati Bengals, according to Harbaugh.
"He's moving toward practice," Harbaugh said. "When the doctors clear him, which we don't know that date or when that's going to happen right now. We believe it's going to be real soon, in time to prepare for Cincinnati and he'll be out there."
Originally, Flacco was only expected to miss the first week of training camp, but trainers and team doctors still have not cleared him to play. The Ravens offense has appeared out of sync for much of the preseason with backup Ryan Mallett taking most of the snaps.
Flacco had an uneven season in 2016 one year removed from season-ending knee surgery. He threw for a franchise-record 4,317 yards with 20 touchdowns, but also had 15 interceptions.
The key now is to get him ready for live snaps less than two weeks away from the start of the season.
"He's been working really hard on it and I do believe he's in good shape," Harbaugh said. "I wouldn't say football shape because he hasn't played football, but he's in really good shape as far as his conditioning, his cardiovascular, his strength and those kinds of things."
After making a 40-yard field goal, Tucker was knocked hard to the ground when trying to tackle Buffalo returner Brandon Tate on the ensuing kickoff. Tucker was woozy when he got to his feet and was placed in concussion protocol.
He was later cleared, but it was the second time this preseason Tucker was knocked around on a kickoff. There are lingering questions as to why Tucker was even that deep down the field, putting himself in harm's way.
The Ravens offense has not inspired any confidence with quarterback Joe Flacco still sidelined with a back injury. Baltimore might have to heavily rely on Tucker's leg to put up points, especially early in the season while Flacco finds his footing.
However, the Ravens don't plan to dramatically alter their coverage plans to protect Tucker, according to head coach John Harbaugh.
"I would prefer that the ball not get to him," Harbaugh said. "That's the responsibility of the rest of the guys - to keep the ball away from him."
Tucker is the most accurate kicker in NFL history with at least 100 attempts, and he would be difficult to replace. Backup kicker Kenny Allen managed a 40-yard field goal in the Ravens' 13-9 victory over Buffalo, but he is still mostly unproven and certainly does not have Tucker's pedigree.
Tucker does not plan to change his approach, despite the injury scares.
"I think I've been involved in five or six or -- you can probably count it on two hands - contact plays in the last five years where I've either had to make a tackle or been hit," Tucker said. "Some of that's admittedly kind of nice about my position. But at the same time, of those seven ... hits I've been involved with, in (the) regular season, both ways it's faster.
"That's probably the only difference is when you get in the regular season is I'm going in to light somebody up. I'm not just trying to make the tackle. I'm trying to do a little bit more than just that."
Notes: Cornerback Brandon Boykin missed his second consecutive practice Tuesday for an undisclosed reason. Boykin is expected to provide valuable depth in the secondary. The Ravens have already lost Tavon Young to a season-ending knee injury and fellow cornerback Maurice Canady has not practiced in three weeks. The Ravens did not provide a timeline for Boykin's return. ... Quarterback Thaddeus Lewis returned to practice Tuesday after sitting out the previous day for undisclosed reasons. If Lewis was unavailable to play in the final preseason game Thursday against the New Orleans Saints, then Josh Woodrum might have played the entire game. Ravens starting quarterback Joe Flacco is out with a back injury and Baltimore does not want to risk an injury to primary backup Ryan Mallett. Lewis was signed Aug. 14 after QB Dustin Vaughan was waived. The Ravens are Lewis' eighth team in the past eight seasons.
Running back Danny Woodhead (hamstring) has missed more than a week of practice after being injured in the second preseason game against the Miami Dolphins. However, the Ravens hope he will be ready for the regular-season opener. Woodhead, 32, signed with the team as a free agent and he is expected to provide added versatility because of his ability to catch the ball out of the backfield. ... Wide receiver Breshad Perriman (hamstring) is on schedule to play in the regular-season opener Sept. 10 against the Bengals, Harbaugh said Tuesday. "That's barring any kind of setback," he warned. Perriman has not practiced since Aug. 1 and has appeared in only one preseason game in his three seasons in Baltimore. Perriman missed his entire rookie season in 2015 with a knee injury.