The exact term hasn't been used, but the indication is Lewis' status will be a game-time decision because of a toe injury that sidelined him for last week's victory over the Cincinnati Bengals.
"I really don't know," Harbaugh told reporters about Lewis' status, according to The Baltimore Sun. "It's not like we've got some secret that we're holding back from anybody on any of these guys. We've got three, four, five guys that are up in the air. Our biggest issue right now is nicks and bumps and bruises."
NFL Network insider Jason La Canfora cited sources in reporting the decision to play Sunday would be up to Lewis.
Lewis released a statement Tuesday saying he would do "everything in my power to get back as fast as I can," and cited progress with the injury. Lewis took part in a limited portion of practice all week and officially was listed Wednesday as questionable to play.