The 32-year-old Ivy, who started a majority of the Ravens games in 2007 opposite Chris McAlister, had 63 tackles, three sacks and an interception that season. His playing time decreased in 2008, and he had just 11 total tackles. He was not re-signed after the season.
"He fits us right now," coach John Harbaugh said during his weekly radio program Tuesday evening. "We need a guy that can play in the slot, the nickel corner position. There was nobody else out there that could do that, and certainly nobody that knows our system. He fits right in, knowing our defense. We're not going to have to teach him the defense, which certainly takes two or three or four weeks if you bring someone in that hasn't been a part of this system before. So Corey's a guy that can play Sunday against the Steelers."
Harbaugh also said that Chris Carr will start at cornerback opposite Domonique Foxworth against Pittsburgh Sunday, a game that could determine whether the Ravens capture their third playoff berth in four years.
Harbaugh said the club chose Ivy over McAlister because of Ivy's familiarity with playing the slot and questions about McAlister's health.
"Playing in the slot is difficult," Harbaugh said. "It's a linebacker position, it's the nickel position. All those things are just some things Chris hasn't done before. So we have to get Chris up to speed if we can get him up to speed. Plus, we do have some concerns about his health. So whether he can play or not and practice and get ready to play in time, that's a concern for us."
Webb, a rookie, suffered a torn anterior cruciate ligament in his right knee Sunday against the Chicago Bears while blocking on special teams. He was placed on injured reserve Tuesday.