Several Ravens who dealt with injuries this offseason have returned to the field at the start of training camp.
But inside linebacker Jameel McClain is not one of them.
Since suffering a spinal cord contusion from a hit he delivered on Dec. 9, McClain has been out for seven and a half months.
Harbaugh said McClain's return date is tough to predict because of the nature of the injury. Back injuries can often take longer to completely heal, and the Ravens want to be very careful when it comes to the spinal cord.
"That just has to heal. Until that heals and we have proof that it's healed, he's not going to be out there," Harbaugh said.
McClain had recently expressed optimism about his chances of returning to the field.
"I'm in shape, I'm working hard, I'm trimming up and getting ready for the season," McClain told The Baltimore Sun. "It's time for gametime. It's in the doctors' hands."
Harbaugh said doctors had anticipated that McClain would be cleared to play by this time.
"It's a little slower, maybe, than we had hoped," he said. "But when he's ready, he'll be out there."
McClain, 27, started all 13 games last year before his injury while playing the Redskins. He made 79 tackles and had three pass deflections.
McClain would be penciled in as a starter upon his return, but if he's not able to play, rookie second-round pick Arthur Brown and free-agent signee Daryl Smith would likely be Baltimore's first-team linebackers.