Veteran cornerback Aaron Ross tore his Achilles tendon while running the Ravens' conditioning test and will miss the remainder of the season.
Ravens coach John Harbaugh announced that Ross suffered the injury Thursday morning as the team started training camp.
Ross signed with the Ravens following his tryout at their June minicamp.
A former first-round draft pick out of Texas, Ross, 31, won a pair of Super Bowl championships with the New York Giants. He played for Ravens secondary coach Steve Spagnuolo as a rookie when the Giants won Super Bowl XLII in 2008.
Ross has played in the NFL for seven seasons. He was placed on injured reserve last year due to a back injury. Ross has 11 career interceptions and 41 passes defended.
Meanwhile, cornerback Dominique Franks didn't pass the Ravens' conditioning test, a series of timed runs, and is being held out of practice until he does. Once players pass the test, they're cleared to practice.
Franks was signed in June following a minicamp audition that included Drayton Florence, Marquice Cole, Bobby Felder, Ross and Kevin Thomas.
The Ravens signed Ross and Franks to provide competition for Chykie Brown and Asa Jackson for the nickel back vacancy created by Corey Graham signing with the Buffalo Bills in March.
Franks, 26, is a 2010 Atlanta Falcons fifth-round draft pick from Oklahoma. The 6-foot, 197-pound defensive back has 30 tackles, three interceptions and nine passes defended in four NFL seasons , including four starts.
Franks played in 15 games last season as a reserve cornerback for Atlanta. The Falcons released him during their final major roster cutdown before re-signing him after he worked out for the Kansas City Chiefs, Miami Dolphins and Pittsburgh Steelers.
Backup nose tackle Terrence Cody remains on the physically unable to perform list after undergoing offseason hip surgery.
Eighty-seven players are practicing Thursday as the Ravens opened camp following an 8-8 season in which the team failed to make the playoffs for the first time in six years.