Johnson played for the New Orleans Saints for the previous three seasons.
He has played in 40 career games.
With the Saints, he had 86 tackles and five sacks.
Last season he had 15 tackles and two sacks.
After originally signing as an undrafted free agent with the Indianapolis Colts in 2006, he spent time in NFL Europe, the Arena Football League and the Canadian Football League before playing in the NFL for the first time in 2011.
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Aaron Wilson covers the Ravens for The Baltimore Sun