Greenwood, who was drafted by the Detroit Lions in the fifth round in 2012 out of Albion College, joins the Ravens after the team placed cornerback Asa Jackson on injured reserve earlier this week. Jackson was the fifth Ravens cornerback to be declared out for the season.
Greenwood, a big cornerback at 6 feet 1, 193 pounds, has played in three career games and has six tackles. Greenwood has run the 40-yard dash in 4.42 seconds.
He also had a stint with the Dallas Cowboys last season, was cut by the Lions in training camp this year and then was signed to the Vikings' practice squad.