Finnegan, 31, will begin playing inside at nickel, battling Colin Jones for snaps. That means Bene' Benwikere will remain the every-down corner with Tillman out indefinitely with what has been called a hyperextended knee.
Here are five things to know about Finnegan, a 2008 Pro Bowl selection who in March announced he was retiring (but never turned in the paperwork):
Dirty player? Finnegan has been called one of the dirtiest players in the NFL. He was ranked the third-dirtiest player in a 2012 midseason poll by The Sporting News. He ranked behind Detroit's Ndamukong Suh and Miami's Richie Incognito.
Crazy? Finnegan was once compared to former Panthers wide receiver Steve Smith in a South Florida Sun Sentinel article titled, "Crazy is the norm for Dolphins' Cortland Finnegan, Baltimore's Steve Smith." Recounting in the 2014 article his first meeting with Smith, Finnegan said, "It's my second year in the league, and he comes over to me and he says, 'None of the crazy stuff, Finnegan.' And I've never played him before, so I'm like, 'Yes sir.' I'm like, 'OK. Nothing crazy. Because back then they called me 'Crazy.'"
Carolina ties: Finnegan was born in Fayetteville, North Carolina, about a three-hour drive from Charlotte. He went to high school in Milton, Florida, before attending college at Samford in Homewood, Alabama. There he became the first Samford player drafted (seventh round, Tennessee in 2006) since Gary Fleming went to Baltimore in 1969.
Super Bowl Shuffle: Carolina coach Ron Rivera is the second member of the 1985 Chicago Bears Super Bowl team for which Finnegan has played. Finnegan played for Jeff Fisher, on injured reserve in Chicago during that 18-1 season, at Tennessee and St. Louis.
The fight: Finnegan is best known by some for his 2010 fight with Houston wide receiver Andre Johnson in which the helmets from both players came off. Both players were fined $25,000. Finnegan took a final shot at Johnson in his March retirement announcement on Instagram, saying Johnson "hits like a bish."