Cook had 120 tackles, 13 pass deflections and one sack in four seasons for the Minnesota Vikings.
He started 29 games for the Vikings, including 11 starts last season.
Gabbert, 24, is a former Missouri standout drafted 10th overall by Jacksonville in 2011.
He has 22 touchdowns in three NFL seasons, passing for 4,357 yards.F
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Aaron Wilson covers the Ravens for The Baltimore Sun